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Sample records for geomagnetic disturbance infradian

  1. Geomagnetic Disturbances Caused by Internal Atmospheric Dynamics

    NASA Technical Reports Server (NTRS)

    Sonneman, G.

    1984-01-01

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

  2. Electric utility industry experience with geomagnetic disturbances

    SciTech Connect

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

    1991-09-01

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

  3. Electric Utility Industry Experience with Geomagnetic Disturbances

    SciTech Connect

    Barnes, P.R.

    1991-01-01

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

  4. Electric utility industry experience with geomagnetic disturbances

    SciTech Connect

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

    1991-09-01

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

  5. Geomagnetic disturbance effects on power systems

    SciTech Connect

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

    1993-07-01

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

  6. Space radiation enhancement linked to geomagnetic disturbances.

    PubMed

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

    1998-01-01

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

  7. The geocoronal responses to the geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Kuwabara, M.; Yoshioka, K.; Murakami, G.; Tsuchiya, F.; Kimura, T.; Yamazaki, A.; Yoshikawa, I.

    2017-01-01

    Atomic hydrogen atoms in the terrestrial exosphere resonantly scatter solar Lyman alpha (121.6 nm) radiation, observed as the hydrogen geocorona. Measurements of scattered solar photons allow us to probe time-varying distributions of exospheric hydrogen atoms. The Hisaki satellite with the extreme ultraviolet spectrometer (EXtreme ultraviolet spectrosCope for ExosphEric Dynamics: EXCEED) was launched in September 2013. EXCEED acquires spectral images (52-148 nm) of the atmospheres/magnetospheres of planets from Earth orbit. Due to its low orbital altitude ( 1000 km), the images taken by the instrument also contain the geocoronal emissions. In this context, EXCEED has provided quasi-continuous remote sensing observations of the geocorona with high temporal resolution ( 1 min) since 2013. These observations provide a unique database to determine the long-term behavior of the exospheric density structure. In this paper, we report exospheric structural responses observed by EXCEED to geomagnetic disturbances. Several geomagnetic storms with decreases of Dst index occurred in February 2014 and the Lyman alpha column brightness on the night side of the Earth increased abruptly and temporarily by approximately 10%. Hisaki reveal that the time lag between the peaks of the magnetic activity and the changes in the Lyman alpha column brightness is found to be about 2 to 6 h during storms. In order to interpret the observational results, we evaluate quantitatively the factors causing the increase. On the basis of these results, a coupling effect via charge exchange between the exosphere and plasmasphere causes variations of the exospheric density structure.

  8. System identification of geomagnetic disturbances initiated by the solar wind.

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaoyan; Tschu, Kangkun

    1991-05-01

    On the basis of linear and time-invariant supposition, the geomagnetic disturbances initiated by the solar wind have been studied in terms of least square non-parametric identification method. The macro-external description of the response of the magnetosphere to the solar wind is given by the impulse response function. The predicted geomagnetic disturbances are compared with the observations; they are found to agree quite well.

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

    PubMed

    Moore, F R

    1977-05-06

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

  10. Geomagnetic disturbances imprints in ground and satellite altitude observatories

    NASA Astrophysics Data System (ADS)

    Yahiat, Yasmina; Lamara, Souad; Zaourar, Naima; Hamoudi, Mohamed

    2016-04-01

    The temporal evolution of the geomagnetic field and its variations have been repeatedly studied from both ground observatories and near-earth orbiting platforms. With the advent of the space ageand the launches of geomagnetic low altitude orbits satellites, a global coverage has been achieved. Since Magsat mission, more satellites were put into orbit and some of them are still collecting data enhancing the spatial and temporal descriptions of the field. Our study uses new data gathered by the latest SWARM satellite mission launched on November, 22nd 2013. It consists of a constellation of three identical satellites carrying on board high resolution and accuracy scientific equipment. Data from this constellation will allow better understanding the multiscale behavior of the geomagnetic field. Our goal is to analyze and interpret the geomagnetic data collected by this Swarm mission, for a given period and try to separate the external disturbances from internal contributions. We consider in the study the variation of the horizontal component H, for different virtual geomagnetic observatories at the satellite altitude. The analysis of data by Swarm orbital segments shows clearly the external disturbances of the magnetic field like that occurring on 27th of August 2014. This perturbation is shown on geomagnetic indexes and is related to a coronal mass ejection (CME). These results from virtual observatories are confirmed, by the equivalent analysis using ground observatories data for the same geographic positions and same epochs. Key words: Geomagnetic field, external field, geomagnetic index, SWARM mission, virtual observatories.

  11. Electric Utility Industry Experience with Geomagnetic Disturbances

    DTIC Science & Technology

    1991-09-01

    the March 13, 1989, geomagnetic storm. Source: North American Electric Reliability Council ................................................ 9 Fig. 2.2...Events and K intensity recorded in North America during the March 13, 1989, geomagnetic storm. Source: North American Electric Reliability Council. 2.2...Unit I experienced VAR excursions of 150 to 200 MVAR. Additional VARs were consumed by the saturated step-up transformers. An empirical equation

  12. Quiet time F2-layer disturbances at geomagnetic equator

    NASA Astrophysics Data System (ADS)

    Depueva, A. Kh.; Mikhailov, A. V.; Depuev, V. Kh.

    2005-03-01

    Ionospheric F2- layer disturbances not related to geomagnetic activity (Q2 disturbances) were analyzed using all available NmF2 observations over Huancayo (American sector) and Kodaikanal (Indian sector) stations located at the proximity of geomagnetic equator. Both positive and negative Q disturbances were revealed, their amplitude being comparable to usual F2 layer storm effects. The occurrence of Q disturbances exhibit a systematic dependence on solar activity, season, and local time. The revealed morphology of Q disturbances at Huancayo can be explained by the observed at Jicamarca E×B vertical drifts. There are some differences between Huancayo and Kodaikanal Q disturbance morphological patterns that cannot be attributed to small differences in E×B vertical drifts in the two longitudinal sectors.

  13. Morphological Investigation of Disturbed Ionosphere during Intense Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Malvi, Bhupendra; Srivastav, Prateek S.; Mansoori, Azad A.; Atulkar, Roshni; Bhardwaj, Shivangi; Purohit, P. K.

    2016-10-01

    Geomagnetic Storms are the disturbed magnetic conditions, influenced and induced by Interplanetary Magnetic Field and the Charged Particle's motion around the Earth, respectively, in Geospace. As the ionosphere is woven by the earth's magnetic field it responds to the change in that. During the geomagnetic storms the filled-in plasma between the magnetic field lines, geomagnetic flux tubes, redistributes itself in effect of the magnetic field forcing. In the present study we have done the investigation of the morphology of the ionosphere over the mid and high latitude regions during intense Geomagnetic Storms. We got fairly convincing results; in three cases decrease of the critical frequency of F2 layer (foF2) and in one case enhancement of the critical frequency of F2 layer (foF2) at mid and high latitudes.

  14. Wavelet-based multiscale analysis of geomagnetic disturbance

    NASA Astrophysics Data System (ADS)

    Zaourar, N.; Hamoudi, M.; Mandea, M.; Balasis, G.; Holschneider, M.

    2013-12-01

    The dynamics of external contributions to the geomagnetic field is investigated by applying time-frequency methods to magnetic observatory data. Fractal models and multiscale analysis enable obtaining maximum quantitative information related to the short-term dynamics of the geomagnetic field activity. The stochastic properties of the horizontal component of the transient external field are determined by searching for scaling laws in the power spectra. The spectrum fits a power law with a scaling exponent β, a typical characteristic of self-affine time-series. Local variations in the power-law exponent are investigated by applying wavelet analysis to the same time-series. These analyses highlight the self-affine properties of geomagnetic perturbations and their persistence. Moreover, they show that the main phases of sudden storm disturbances are uniquely characterized by a scaling exponent varying between 1 and 3, possibly related to the energy contained in the external field. These new findings suggest the existence of a long-range dependence, the scaling exponent being an efficient indicator of geomagnetic activity and singularity detection. These results show that by using magnetogram regularity to reflect the magnetosphere activity, a theoretical analysis of the external geomagnetic field based on local power-law exponents is possible.

  15. Ionospheric and geomagnetic disturbances during the 2005 Sumatran earthquakes

    NASA Astrophysics Data System (ADS)

    Hasbi, Alina Marie; Momani, Mohammed Awad; Mohd Ali, Mohd Alauddin; Misran, Norbahiah; Shiokawa, Kazuo; Otsuka, Yuichi; Yumoto, Kiyohumi

    2009-12-01

    This paper investigates the ionospheric and geomagnetic responses during the 28 March 2005 and 14 May 2005 Sumatran earthquakes using GPS and magnetometer stations located in the near zone of the epicenters. These events occurred during low solar and geomagnetic activity. TEC oscillations with periods of 5-10 min were observed about 10-24 min after the earthquakes and have horizontal propagation velocities of 922-1259 m/s. Ionospheric disturbances were observed at GPS stations located to the northeast of the epicenters, while no significant disturbances were seen relatively east and south of the epicenters. The magnetic field measurements show rapid fluctuations of 4-5 s shortly after the earthquake, followed by a Pc5 pulsation of 4.8 min about 11 min after the event. The correlation between the ionospheric and geomagnetic responses shows a good agreement in the period and time lag of the peak disturbance arrival, i.e. about 11-13 min after the earthquake.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    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.

  17. Power grid disturbances and polar cap index during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2013-06-01

    The strong geomagnetic storm in the evening of 30 October 2003 caused high-voltage power grid disturbances in Sweden that expanded to produce hour-long power line outage in Malmö located in the southern part of the country. This was not a unique situation. The 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. These high-voltage power grid disturbances were related to impulsive magnetic variations accompanying extraordinarily intense substorm events. The events were preceded by lengthy intervals of unusually high values of the Polar Cap (PC) index caused by enhanced transpolar ionospheric convection. The transpolar convection transports magnetic flux from the dayside to nightside which causes equatorward displacements of the region of auroral activity enabling the substorms to hit vital power grids. During the 30 October 2003 event the intense solar proton radiation disabled the ACE satellite observations widely used to provide forecast of magnetic storm events. Hence in this case the alarmingly high PC index could provide useful warning of the storm as a back-up of the missing ACE-based forecast. In further cases, monitoring the PC index level could provide supplementary storm warnings to the benefit of power grid operators.

  18. Anomalous phenomena on HF radio paths during geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskii, D. V.

    2016-07-01

    We analyze ionospheric oblique sounding data on three high-latitude and one high-latitude-midlatitude HF radio paths for February 15 and 16, 2014, when two substorms and one magnetic storm occurred. We investigate cases of anomalous propagation of signals: their reflection from sporadic layer Es, lateral reflections, type "M" or "N" modes, the presence of traveling ionospheric disturbances, and the diffusivity of signals and triplets. The most significant results are the following. In geomagnetically undisturbed times, sporadic Es-layers with reduced maximum observed frequencies (MOF Es) on three high-latitude paths were observed in both days. The values of MOF Es during disturbances are large, which leads to the screening of other oblique sounding signals reflected from the ionosphere. On all four paths, the most frequently traveling ionospheric disturbances due to the terminator were observed in quiet hours from 03:00 to 15:00 UT on the first day and from 06:00 to 13:00 UT on the second day of the experiment. In addition, both the sunset terminator and the magnetic storm on the high-latitude-mid-latitude path were found to generate traveling ionospheric disturbances jointly. No such phenomenon was found on high-latitude paths.

  19. Coseismic ionospheric and geomagnetic disturbances caused by great earthquakes

    NASA Astrophysics Data System (ADS)

    Hao, Yongqiang; Zhang, Donghe; Xiao, Zuo

    2016-04-01

    Despite primary energy disturbances from the Sun, oscillations of the Earth surface due to a large earthquake will couple with the atmosphere and therefore the ionosphere, then the so-called coseismic ionospheric disturbances (CIDs) can be detected in the ionosphere. Using a combination of techniques, total electron content, HF Doppler, and ground magnetometer, a new time-sequence of such effects propagation were developed on observational basis and ideas on explanation provided. In the cases of 2008 Wenchuan and 2011 Tohoku earthquakes, infrasonic waves accompanying the propagation of seismic Rayleigh waves were observed in the ionosphere by all the three kinds of techniques. This is the very first report to present CIDs recorded by different techniques at co-located sites and profiled with regard to changes of both ionospheric plasma and current (geomagnetic field) simultaneously. Comparison between the oceanic (2011 Tohoku) and inland (2008 Wenchuan) earthquakes revealed that the main directional lobe of latter case is more distinct which is perpendicular to the direction of the fault rupture. We argue that the different fault slip (inland or submarine) may affect the way of couplings of lithosphere with atmosphere. References Zhao, B., and Y. Hao (2015), Ionospheric and geomagnetic disturbances caused by the 2008 Wenchuan earthquake: A revisit, J. Geophys. Res. Space Physics, 120, doi:10.1002/2015JA021035. Hao, Y. Q., Z. Xiao, and D. H. Zhang (2013), Teleseismic magnetic effects (TMDs) of 2011 Tohoku earthquake, J. Geophys. Res. Space Physics, 118, 3914-3923, doi:10.1002/jgra.50326. Hao, Y. Q., Z. Xiao, and D. H. Zhang (2012), Multi-instrument observation on co-seismic ionospheric effects after great Tohoku earthquake, J. Geophys. Res., 117, A02305, doi:10.1029/2011JA017036.

  20. 77 FR 22312 - Geomagnetic Disturbances to the Bulk-Power System; Notice of Technical Conference

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-13

    ... Energy Regulatory Commission Geomagnetic Disturbances to the Bulk-Power System; Notice of Technical Conference Take notice that the Federal Energy Regulatory Commission staff will hold a Staff Technical Conference on Geomagnetic Disturbances to the Bulk-Power System on Monday, April 30, 2012, from 11 a.m. to...

  1. Search for correlation between geomagnetic disturbances and mortality

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  2. The disturbances of ionospheric Total Electron Content during great geomagnetic storm above Iraq

    NASA Astrophysics Data System (ADS)

    Al-Ubaidi, Najat

    2016-07-01

    Several efforts have been made to study the behavior of Total Electron Content (TEC) with many types of geomagnetic storms; the purpose of this research is to study the disturbances of the ionosphere through the TEC parameter during great geomagnetic storm. TEC data selected for year 2003 (descending solar cycle 23), as available from (www.ngdc.noaa.gov/stp/IONO/USTEC/) for Iraq region (longitude 27-54 degree East, latitude 27-42 degree North) during great geomagnetic storm for 28-30 October 2003. To find out the type of geomagnetic storms the Disturbance storm time (Dst) index was selected for the days selected from Kyoto/Japan website. From data analysis, it is found that in general, there is a good proportionality between disturbance storm time index (Dst) and the total electron contents, the values of TEC in daytime greater than night time, but there is anomaly when the storm continued for several hours from the day.

  3. Search for correlation between geomagnetic disturbances and mortality

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  4. Human physiological reaction to geomagnetic disturbances of solar origin

    NASA Astrophysics Data System (ADS)

    Dimitrova, Sv.; Stoilova, I.

    2002-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Rollison, Eric; Moura, John; Lauby, Mark

    2011-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  7. 77 FR 24952 - Staff Technical Conference on Geomagnetic Disturbances to the Bulk-Power System; Technical...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-26

    ... Energy Regulatory Commission Staff Technical Conference on Geomagnetic Disturbances to the Bulk-Power System; Technical Conference Agenda As announced in the Notice of Technical Conference issued on April 6, 2012, the Commission Staff will hold a technical conference on Monday, April 30, 2012, from 11:00...

  8. Uncovering the nonadiabatic response of geosynchronous electrons to geomagnetic disturbance

    USGS Publications Warehouse

    Gannon, Jennifer; Elkington, Scot R.; Onsager, Terrance G.

    2012-01-01

    We describe an energy spectrum method for scaling electron integral flux, which is measured at a constant energy, to phase space density at a constant value of the first adiabatic invariant which removes much of the variation due to reversible adiabatic effects. Applying this method to nearly a solar cycle (1995 - 2006) of geosynchronous electron integral flux (E>2.0MeV) from the GOES satellites, we see that much of the diurnal variation in electron phase space density at constant energy can be removed by the transformation to phase space density at constant μ (4000 MeV/G). This allows us a clearer picture of underlying non-adiabatic electron population changes due to geomagnetic activity. Using scaled phase space density, we calculate the percentage of geomagnetic storms resulting in an increase, decrease or no change in geosynchronous electrons as 38%, 7%, and 55%, respectively. We also show examples of changes in the electron population that may be different than the unscaled fluxes alone suggest. These examples include sudden electron enhancements during storms which appear during the peak of negative Dst for μ-scaled phase space density, contrary to the slow increase seen during the recovery phase for unscaled phase space density for the same event.

  9. The effect of cosmic ray intensity variations and geomagnetic disturbances on the physiological state of aviators

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

    Over the last few years various researches have reached the conclusion that cosmic ray variations and geomagnetic disturbances are related to the condition of the human physiological state. In this study medical data regarding 4018 Slovak aviators were analyzed in relation to daily variations of cosmic ray and geomagnetic activity. Specifically daily data concerning mean values of heart rate which were registered during the medical examinations of the Slovak aviators, were related to daily variations of cosmic ray intensity, as measured by the Neutron Monitor Station on Lomnicky Stit (http://neutronmonitor.ta3.sk/realtime.php3) and the high resolution neutron monitor database (http://www.nmdb.eu) and daily variations of Dst and Ap geomagnetic indices. All subjects were men in good health of age 18-60 yrs. This particular study refers to the time period from 1 January 1994 till 31 December 2002. Statistical methods were applied to establish a statistical significance of the effect of geomagnetic activity levels and cosmic ray intensity variations on the aforementioned physiological parameters for the whole group. The Pearson r-coefficients were calculated and the Analysis of Variance (ANOVA) method was applied to establish the statistical significance levels (p-values) of the effect of geomagnetic activity and cosmic ray intensity variations on heart rate up to three days before and three days after the respective events. Results show that there is an underlying effect of geomagnetic activity and cosmic ray intensity variations on the cardiovascular functionality.

  10. Role of geomagnetic disturbance on whistler occurrence at a low latitude station

    NASA Astrophysics Data System (ADS)

    Singh, Shubha; Patel, R. P.; Singh, Krishna K.; Singh, A. K.; Singh, R. P.

    2007-07-01

    In this paper, we report the results derived from a statistical analysis of whistlers recorded at Varanasi during the period January 1990-December 1999. The monthly occurrence rate shows a maximum during January to March. In order to study the role of geomagnetic disturbance on the whistler occurrence rate, we have used the KP index and its variation. It is found that the occurrence probability monotonically increases with ∑ KP (daily sum) values. It is found that, when ∑ KP>20, the occurrence rate is greater than the average value, in good agreement with results reported by other workers. In addition, we also present the probability of the observation of whistlers during weak/intense geomagnetic storms and also during the main phase and recovery phase of geomagnetic storms.

  11. Disturbance dynamo electric fields in response to geomagnetic storms occurring at different universal times

    NASA Astrophysics Data System (ADS)

    Huang, C.

    2013-12-01

    Perturbed electric fields in the earth's ionosphere, resulting from the penetration electric fields from high latitudes and/or from the dynamo mechanism driven by the neutral disturbances, occurr in the storm periods. In general, the identification of the penetration electric fields is easier than that of the dynamo electric fields. At times, the latter becomes unperceivable or difficult to identify. This is an interesting problem which motivates a model study to investigate the possible reasons. Model runs made with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (NCAR/TIEGCM) will be presented. Theoretical studies of ionospheric responses to geomagnetic storms with model simulations indicate that the intensities of disturbance dynamo electric fields are highly dependent on various parameters such as solar activities, seasonal effects and universal times, etc. When geomagnetic storms commence at 01~07 UT in summer solstices with low solar fluxes, the disturbance dynamo electric fields become very small. As compared with the general daily variations, they seem to be unperceivable. This phenomenon can be explained by the model results which show that the positive charge accumulation at low latitudes will be weakened when the equatward neutral disturbances penetrate into the opposite hemisphere in the storm time. For other cases, the magnitudes of the dynamo electric fields are relatively larger under the same geomagnetic activity.

  12. The effects of geomagnetic disturbances on electrical systems at the earth's surface

    NASA Astrophysics Data System (ADS)

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

    Geomagnetic disturbances have affected electrical systems on the ground for over 150 years. The first effects were noted on the early telegraph in the 1840s and in this century magnetic storms have caused power system blackouts and phone system outages. Affected systems include all those that use electrical conductors: whether for transmission of power or signals or where the conducting properties are incidental to their use such as with pipelines and railway tracks. In power systems geomagnetically induced currents cause partial saturation of power transformers producing transformer heating and distortion of the ac waveform leading to misoperation of relays and other equipment. On pipelines, induced currents may contribute to corrosion but also present a problem with the electrical surveys of the pipe performed to monitor the corrosion prevention systems. Severity of these effects depends on disturbance size, proximity to the auroral zone, and the conductivity structure of the Earth. Also significant are system parameters such as the use of higher resistance coatings on pipelines and the linking of power systems into larger networks. In this paper we have attempted to catalogue all the published reports of geomagnetic effects on electrical systems and show their occurrence in the context of the solar cycle and geomagnetic activity variations for the years 1844 to 1996.

  13. Case study of psychophysiological diary: infradian rhythms.

    PubMed

    Slover, G P; Morris, R W; Stroebel, C F; Patel, M K

    1987-01-01

    A 4-year case study was made of a 42-year-old white woman as seen through the psychophysiological diary. There was an awakening diary and a bedtime diary composed of 125 variables. The data are divided into two series: series I containing a manic episode, and series II as a control. Spectral analysis shows infradian rhythms in hypoglycemia and fear (11 days) and time to fall asleep (5 days). Depressed feelings showed a circatrigintan (28-day) rhythm, which was not correlated with menses. Mania had an annual rhythm (spring) but no circatrigintan or less rhythm. The following correlations have a P value less than or equal to 0.01: mania was directly correlated with number of sleeping pills, time to really wake up, need for rest, moodiness, and helplessness, and indirectly with expectations, pressure at work, sense of time, and emotional state. Interestingly, awakening pulse is directly correlated with awakening temperature, number of sleeping pills, bedtime pulse, tiredness at bedtime, hypoglycemia, and fear. Bedtime pulse is directly correlated with awakening pulse and awakening temperature. Both pulse and temperature at bedtime are directly correlated with negative variables such as tiredness, moodiness, helplessness, and depression, and inversely correlated with positive variables such as happiness, loving, performance at work, and thinking efficiency. This study demonstrates a significant correlation between physiological variables.

  14. Role of Geomagnetic Disturbances on VLF Whistler Wave Activity at Low Latitudes (P32)

    NASA Astrophysics Data System (ADS)

    Patel, R. P.; Singh, S.; Singh, A. K.; Singh, R. P.

    2006-11-01

    rppatel123@rediffmail.com The disturbances on solar surfaces lead to the enhanced injection of energetic charged particles in to the inner magnetosphere, which modifies the electrodynamic features of ionosphere and magnetosphere. The electrodynamic properties control the generation and propagation characteristics of VLF waves. At Varanasi station, which is one of the low latitude stations in India, we have recorded VLF waves from 1992 onwards. The source of VLF wave is natural lightning discharges. Whistler activity varies with latitude having maximum around 500 geomagnetic latitude. The occurrence rate is low at low latitudes and also depends on the solar and geomagnetic conditions. In this paper, we report the results derived from the statistical analysis of whistler waves recorded at Varanasi during the period January 1990 December 1999. The monthly occurrence rate is obtained which shows maximum during January to March. Seasonal variation of the occurrence rate is also studied. In order to study the role of geomagnetic disturbances on the occurrence rate, we have used Kp index and its variation. It is observed that the occurrence probability monotonically increases with ∑Kp values. It is observed that when ∑Kp > 10, the occurrence rate is greater than the average value. This tendency is found to be in good agreement with those reported by other workers. In addition, we also present the probability of observation of whistler waves during the weak/intense geomagnetic storm. Detailed result of occurrence of whistler waves during the main phase and recovery phase of geomagnetic storms will also be presented. An attempt will be made to present explanation of these statistical results.

  15. Application of the SP algorithm to the INTERMAGNET magnetograms of the disturbed geomagnetic field

    NASA Astrophysics Data System (ADS)

    Sidorov, R. V.; Soloviev, A. A.; Bogoutdinov, Sh. R.

    2012-05-01

    The algorithmic system developed in the Laboratory of Geoinformatics at the Geophysical Center, Russian Academy of Sciences, which is intended for recognizing spikes on the magnetograms from the global network INTERMAGNET provides the possibility to carry out retrospective analysis of the magnetograms from the World Data Centers. Application of this system to the analysis of the magnetograms allows automating the job of the experts-interpreters on identifying the artificial spikes in the INTERMAGNET data. The present paper is focused on the SP algorithm (abbreviated from SPIKE) which recognizes artificial spikes on the records of the geomagnetic field. Initially, this algorithm was trained on the magnetograms of 2007 and 2008, which recorded the quiet geomagnetic field. The results of training and testing showed that the algorithm is quite efficient. Applying this method to the problem of recognizing spikes on the data for periods of enhanced geomagnetic activity is a separate task. In this short communication, we present the results of applying the SP algorithm trained on the data of 2007 to the INTERMAGNET magnetograms for 2003 and 2005 sampled every minute. This analysis shows that the SP algorithm does not exhibit a worse performance if applied to the records of a disturbed geomagnetic field.

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

    NASA Astrophysics Data System (ADS)

    Su, F.

    2014-12-01

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

  17. Determination of Geomagnetically Quiet Time Disturbances of the Ionosphere over Uganda during the Beginning of Solar Cycle

    NASA Astrophysics Data System (ADS)

    Habyarimana, Valence

    2016-07-01

    The ionosphere is prone to significant disturbances during geomagnetically active and quiet conditions. This study focused on the occurrence of ionospheric disturbances during geomagnetically quiet conditions. Ionospheric data comprised of Global Positioning System (GPS)-derived Total Electron Content (TEC), obtained over Mt. Baker, Entebbe, and Mbarara International Global Navigation Satellite System (GNSS) Service (IGS) stations. The Disturbance storm time (Dst) index was obtained from Kyoto University website. The number of geomagnetically quiet days in the period under study were first identified. Their monthly percentages were compared for the two years. The monthly percentage of geomagnetically quiet days for all the months in 2009 numerically exceeded those in 2008. December had the highest percentage of geomagnetically quiet days for both years (94 % in 2008 and 100 % in 2009). Geomagnetically quiet days did not show seasonal dependence. The variation in percentage of geomagnetically quiet days during solstice months (May, June, July, November, December, and January) and equinoctial months (February, March, April, August, September, and October) was not uniform. Geomagnetically quiet time disturbances were found to be more significant from 09:00 UT to 13:00 UT. However, there were some other disturbances of small scale amplitude that occurred between 14:00 UT and 22:00 UT. Further analysis was done to identify the satellites that observed the irregularities that were responsible for TEC perturbations. Satellites are identified by Pseudo Random Numbers (PRNs). The ray path between individual PRNs and the corresponding receivers were analysed. Satellites with PRNs: 3, 7, 8, 19 and 21 registered most of the perturbations. It was found that Q disturbances led to fluctuations in density gradients. Significant TEC perturbations were observed on satellite with PRN 21 with receivers at Entebbe and Mbarara on June 28, 2009 between 18:00 UT and 21:00 UT.

  18. Observations of unusual pre-dawn response of the equatorial F-region during geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Lima, W.; Becker-Guedes, F.; Fagundes, P.; Sahai, Y.; Abalde, J.; Pillat, V.

    It is known that the disturbed solar wind-magnetosphere interactions have important effects on equatorial and low-latitude ionospheric electrodynamics. The response of equatorial ionosphere during storm-time is an important aspect of space weather studies. It has been observed that during geomagnetic disturbances both suppression as well as generation of equatorial spread-F (ESF) or plasma irregularities takes place. However, the mechanism(s) associated with the generation of ESF still needs further investigations. This work reports some unusual events of pre-dawn occurrence of ionospheric F-region satellite traces followed by spread-F and cusp-like spread-F from ionospheric sounding observations carried out by a Canadian Advanced Digital Ionosonde (CADI) localized at Palmas (10.2°, 48.2°W, dip latitude 5.7°S), Brazil during 2002, every 5 minutes. For the present work we have scaled and analyzed the ionospheric sounding data for three events (April 20, September 04 and 08, 2002), which are associated with geomagnetic disturbances. In the events studied, the ionograms show the occurrence of satellite trace followed by cusp-like spread. The cusp like features move up in frequency and height and finally attain the F-layer peak value (foF2) and then disappear. They had duration of about 30 min and always occurred in the early morning hours. Our studies involved seven geomagnetic disturbances as well as quiet days during the year 2002, but only on these three occasions we observed these features. We present and discuss these observations in this paper and suggest possible mechanisms for the occurrence of these unusual features.

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

    PubMed

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

    1994-01-01

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

  20. Geomagnetic signatures of sudden ionospheric disturbances during extreme solar radiation events

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Yeh, H.-C.

    2008-12-01

    We performed a comparative study of geomagnetic variations, which are associated with sudden ionospheric disturbances (SIDs) caused by great X-class solar flares on July 14, 2000 (Bastille flare) and on October 28, 2003 (Halloween flare). Intense fluxes of solar X-rays and EUV radiation as well as solar energetic particles (SEP) were considered as sources of abundant ionization of the ionosphere and upper atmosphere. Flare-initiated SIDs are revealed as transient geomagnetic variations, which are generated by enhanced electric currents flowing mainly in the bottom-side ionosphere. Those so-called solar flare effects (SFEs) were studied by using of geomagnetic data from INTERMAGNET worldwide network of ground-based magnetometers. In subsolar region the SFE is mainly controlled by the flare X-rays and/or EUV radiation. We found that in the Halloween flare the contribution of X-rays was comparable with the EUV, but in the Bastille flare the EUV flux was dominant. The ionization at high latitudes is generated by the SEP, which energy flux is comparable and even exceeds the solar electromagnetic radiation in that region. It was shown that in the Halloween event the pattern of SFE is formed by a two-vortex current system, which is similar to the quiet day Sq current system. However, during the Bastille flare, the pattern of induced currents is quite different: the northern vortex shifts westward and southern vortex shifts eastward such that the electroject is substantially tilted relative to the geomagnetic equator. From numerical estimations we found that at middle latitudes the SEP-initiated geomagnetic effect becomes comparable with the effects of solar electromagnetic radiation. It was also shown that the SEP contribute to the SFE in the nightside hemisphere. The revealed features of the SEP impact to the ionosphere were found in a good agreement with the theory of energetic particle penetration to the bottom-side magnetosphere.

  1. Variation of surface electric field during geomagnetic disturbed period at Maitri, Antarctica

    NASA Astrophysics Data System (ADS)

    Victor, N. Jeni; Panneerselvam, C.; Anil Kumar, C. P.

    2015-12-01

    The paper discusses on the variations of the atmospheric vertical electric field measured at sub-auroral station Maitri (70∘75'S, 11∘75'E), and polar station Vostok (78.5∘S, 107∘E) during the geomagnetic disturbances on 25-26 January 2006. Diurnal variation of surface electric field measured at Maitri shows a similar variation with worldwide thunderstorm activity, whereas the departure of the field is observed during disturbed periods. This part of the field corresponds to the magnetospheric/ionospheric (an additional generator in the polar regions) voltage generators. Solar wind parameters and planetary indices represent the temporal variation of the disturbances, and digital fluxgate magnetometer variation continuously monitored to trace the auroral movement at Maitri. We have observed that the electrojet movement leaves its signature on vertical and horizontal components of the DFM in addition; the study infers the position of auroral current wedge with respect to Maitri. To exhibit the auroral oval, OVATION model is obtained with the aid of DMSP satellite and UV measurements. It is noted that the Maitri is almost within the auroral oval during the periods of disturbances. To examine the simultaneous changes in the vertical electric field associated with this magnetic disturbance, the dawn-dusk potential is studied for every UT hours; the potential was obtained from Weimer model and SuperDARN radar. The comparison reveals the plausible situation for the superposition of dawn-dusk potential on surface electric field over Maitri. This observation also shows that the superposition may not be consistent with the phase of the electrojet. Comparison of surface electric field at Maitri and Vostok shows that the parallel variation exhibits with each other, but during the period of geomagnetic disturbances, the influence is not much discerned at Vostok.

  2. Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes

    NASA Astrophysics Data System (ADS)

    Doumbia, Vafi; Boka, Kouadio; Kouassi, Nguessan; Didier Franck Grodji, Oswald; Amory-Mazaudier, Christine; Menvielle, Michel

    2017-01-01

    In this study we examined the influences of geomagnetic activity on the Earth surface electric field variations at low latitudes. During the International Equatorial Electrojet Year (IEEY) various experiments were performed along 5° W in West Africa from 1992 to 1995. Among other instruments, 10 stations equipped with magnetometers and telluric electric field lines operated along a meridian chain across the geomagnetic dip equator from November 1992 to December 1994. In the present work, the induced effects of space-weather-related geomagnetic disturbances in the equatorial electrojet (EEJ) influence area in West Africa were examined. For that purpose, variations in the north-south (Ex) and east-west (Ey) components of telluric electric field were analyzed, along with that of the three components (H, D and Z) of the geomagnetic field during the geomagnetic storm of 17 February 1993 and the solar flare observed on 4 April 1993. The most important induction effects during these events are associated with brisk impulses like storm sudden commencement (ssc) and solar flare effect (sfe) in the geomagnetic field variations. For the moderate geomagnetic storm that occurred on 17 February 1993, with a minimum Dst index of -110 nT, the geo-electric field responses to the impulse around 11:00 LT at LAM are Ex = 520 mV km-1 and Ey = 400 mV km-1. The geo-electric field responses to the sfe that occurred around 14:30 LT on 4 April 1993 are clearly observed at different stations as well. At LAM the crest-to-crest amplitude of the geo-electric field components associated with the sfe are Ex = 550 mV km-1 and Ey = 340 mV km-1. Note that the sfe impact on the geo-electric field variations decreases with the increasing distance of the stations from the subsolar point, which is located at about 5.13° N on 4 April. This trend does not reflect the sfe increasing amplitude near the dip equator due the high Cowling conductivity in the EEJ belt.

  3. Mid-latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Astrophysics Data System (ADS)

    Minow, J. I.; Willis, E. M.; Parker, L. N.

    2014-12-01

    Spacecraft charging of the International Space Station (ISS) is dominated by the interaction of the high voltage US solar arrays with the F2-region ionospheric plasma environment. We are working to fully understand the charging behavior of the ISS solar arrays and determine how well future charging behavior can be predicted from in-situ measurements of plasma density and temperature. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that may be encountered at ISS orbital altitudes (~400 km), the latitudes over which they occur, and the time periods for which the disturbances persist. We will present preliminary results from a study of ionospheric disturbances in the "mid-latitude" region defined as the ~30 degree to ~60 degree extra-equatorial magnetic latitudes sampled by ISS. The study is focused on geomagnetic storm periods because they are well known drivers for disturbances in the high-latitude and mid-latitude ionospheric plasma. Changes in the F2 peak electron density obtained from ground based ionosonde records are compared to in-situ electron density and temperature measurements from the CHAMP and ISS spacecraft at altitudes near, or above, the F2 peak. Results from a number of geomagnetic storms will be presented and their potential impact on ISS charging will be discussed.

  4. Modeling of ionospheric irregularities during geomagnetically disturbed conditions over African low-latitude region

    NASA Astrophysics Data System (ADS)

    Mungufeni, Patrick; Habarulema, John Bosco; Jurua, Edward

    2016-10-01

    In this study, station-specific models of ionospheric irregularities over low-latitude African region during geomagnetically disturbed days (Dst≤-50 nT) have been developed. Global Navigation Satellite Systems (GNSS)-derived ionospheric total electron content (TEC) data during 1998-2014 were used. Ionospheric irregularities were represented with the rate of change of TEC index (ROTI). The inputs for the models are the local time, solar flux index, day number of the year, auroral electrojet, and the disturbance storm time indices, while the output is the hourly median ROTI during these given conditions. To develop the models, the ROTI index values were binned based on the input parameters and cubic B splines were then fitted to the binned data. Developed models were validated with independent data over stations within 680 km radius. The models reproduced fairly well the inhibitions and the occurrences of ionospheric irregularities during geomagnetically disturbed days. The models even emulated these patterns in the various seasons, during medium and high solar activity conditions. During validations of the models, the percentages of the number of errors (difference between the observed and the modeled ROTI) <0.05 total electron content unit, 1TECU = 1016 el m-2 (TECU)/Min at all the stations were all >70% and the root-mean-square error were mostly < 0.1 TECU/Min. Furthermore, the correlation coefficients ranged from 0.47 to 0.76.

  5. Co-located ionospheric and geomagnetic disturbances caused by great earthquakes

    NASA Astrophysics Data System (ADS)

    Hao, Yongqiang; Zhang, Donghe; Xiao, Zuo

    2016-07-01

    Despite primary energy disturbances from the Sun, oscillations of the Earth surface due to a large earthquake will couple with the atmosphere and therefore the ionosphere, to generate so-called coseismic ionospheric disturbances (CIDs). In the cases of 2008 Wenchuan and 2011 Tohoku earthquakes, infrasonic waves accompanying the propagation of seismic Rayleigh waves were observed in the ionosphere by a combination of techniques, total electron content, HF Doppler, and ground magnetometer. This is the very first report to present CIDs recorded by different techniques at co-located sites and profiled with regard to changes of both ionospheric plasma and current (geomagnetic field) simultaneously. Comparison between the oceanic (2011 Tohoku) and inland (2008 Wenchuan) earthquakes revealed that the main directional lobe of latter case is more distinct which is perpendicular to the direction of the fault rupture. We argue that the different fault slip (inland or submarine) may affect the way of couplings of lithosphere with atmosphere. Zhao, B., and Y. Hao (2015), Ionospheric and geomagnetic disturbances caused by the 2008 Wenchuan earthquake: A revisit, J. Geophys. Res., doi:10.1002/2015JA021035. Hao, Y. Q., et al. (2013), Teleseismic magnetic effects (TMDs) of 2011 Tohoku earthquake, J. Geophys. Res., doi:10.1002/jgra.50326. Hao, Y. Q., et al. (2012), Multi-instrument observation on co-seismic ionospheric effects after great Tohoku earthquake, J. Geophys. Res., doi:10.1029/2011JA017036.

  6. Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Willis, Emily M.; Parker, Linda Neergaard

    2014-01-01

    Spacecraft charging of the International Space Station (ISS) is dominated by the interaction of the high voltage US solar arrays with the F2-region ionospheric plasma environment. We are working to fully understand the charging behavior of the ISS solar arrays and determine how well future charging behavior can be predicted from in-situ measurements of plasma density and temperature. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that may be encountered at ISS orbital altitudes (approximately 400 km), the latitudes over which they occur, and the time periods for which the disturbances persist. We will present preliminary results from a study of ionospheric disturbances in the "mid-latitude" region defined as the approximately 30 - 60 degree extra-equatorial magnetic latitudes sampled by ISS. The study is focused on geomagnetic storm periods because they are well known drivers for disturbances in the high-latitude and mid-latitude ionospheric plasma. Changes in the F2 peak electron density obtained from ground based ionosonde records are compared to in-situ electron density and temperature measurements from the CHAMP and ISS spacecraft at altitudes near, or above, the F2 peak. Results from a number of geomagnetic storms will be presented and their potential impact on ISS charging will be discussed.

  7. Modeling the Impacts of Geomagnetic Disturbances on the New York State Power Transmission System

    NASA Astrophysics Data System (ADS)

    Ouedraogo, D.; Castillo, O. L.; Mohamed, A.; Damas, M. C.; Ngwira, C. M.

    2015-12-01

    Our society today relies heavily on electricity in order to meet its essential basic needs. However, to meet the rising demands for this energy, all power companies require smooth and efficient delivery of services to the consumers. The US power grid is a complex electrical apparatus that has well known sensitivities to space weather disturbances. Events produced by space weather includes solar storms or geomagnetic disturbances [GMD]. The propagation of such events in the direction of Earth perturbs the electric currents in the magnetosphere and the ionosphere, causing a unique effect known as a Geomagnetically Induced Current [GIC]. GICs are known to saturate and overheat transformers in the power grid, threatening the safe operation of the power system. A GMD induces a geoelectric field in high-voltage and extra high-voltage transmission circuits. This geoelectric field represents electromotive force, and causes GICs to circulate through transmission circuits and transformers. Power models are being developed using MATLAB/Simulink® software to simulate the propagation of GIC flows in a power system, while using New York State (NYS) power transmission network as an example. We will present results of the models used to assess the impacts of possible GMD strikes on the various parts of the power network.

  8. A local ionospheric model for forecasting the critical frequency of the F2 layer during disturbed geomagnetic and ionospheric conditions

    NASA Astrophysics Data System (ADS)

    Pietrella, M.; Perrone, L.

    2008-02-01

    An ionospheric forecasting empirical local model over Rome (IFELMOR) has been developed to predict the state of the critical frequency of the F2 layer (foF2) during geomagnetic storms and disturbed ionospheric conditions. Hourly measurements of foF2 obtained at the Rome observatory, hourly quiet-time values of foF2 (foF2QT), and the hourly time-weighted accumulation series derived from the geomagnetic planetary index ap (ap(τ)), were considered during the period January 1976-December 2003. Under the assumption that the ionospheric disturbance index log(foF2/foF2QT) is correlated to the integrated geomagnetic index ap(τ), statistically significant regression coefficients are obtained for different months and for different ranges of ap(τ) and used as input to calculate the short-term ionospheric forecasting of foF2. The empirical storm-time ionospheric correction model (STORM) was used to make comparisons with the IFELMOR model. A few comparisons between STORM's performance, IFELMOR's performance, the median measurements and the foF2QT values, were made for significant geomagnetic storm events (ap>150) occurring from 2000 to 2003. The results provided by IFELMOR are satisfactory, in particular, for periods characterized by high geomagnetic activity and very disturbed ionospheric conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  10. Formation of Polar Ionospheric Tongue of Ionization during Minor Geomagnetic Disturbed Conditions

    NASA Astrophysics Data System (ADS)

    Liu, J.; Wang, W.; Burns, A. G.; Yue, X.; Zhang, S.; Zhang, Y.

    2015-12-01

    Previous investigations of ionospheric storm-enhanced density (SED) and tongue of ionization (TOI) focused mostly on the behavior of TOI during intense geomagnetic storms. Little attention has been paid to the spatial and temporal variations of TOI during weak to moderate geomagnetic disturbed conditions. we investigate the source and development of TOI during a moderate geomagnetic storm on 14 October 2012.Multi-instrumental observations including GPS total electron content (TEC), Defense Meteorological SatelliteProgram(DMSP) in situ measured total ion concentration and ion drift velocity, SuperDARN measured polar ionconvection patterns, and electron density profiles from the Poker Flat Incoherent Scatter Radar (PFISR) have been utilized in the current analysis. GPS TEC maps show salient TOI structures persisting for about 5 h over high latitudes of North America on 14 October 2012 in the later recovery phase of the storm when the magnitudes of IMF By and Bz were less than 5 nT. The PFISR electron density profiles indicate that the extra ionization for TEC enhancements mainly occurred in the topside ionosphere with no obvious changes in the bottom side ionosphere and vertical plasma drifts. Additionally, there were no signatures of penetration electric fields in the equatorial electrojet data and upward ion drifts at high latitudes. At the same time, strong subauroral polarization streams with ion drift speeds exceeding 2.5 km/s carried sunward fluxes and migrated toward lower latitudes for about 5° based on the DMSP cross-track driftmeasurements. Based on those measurements,we postulate that the combined effects of initial build-up of ionization at midlatitudes through daytime production of ionization and equatorward (or less poleward than normal daytime) neutral wind reducing downward diffusion along the inclined filed lines, and an expanded polar ion convection pattern and its associated horizontal plasma transport are important in the formation of the TOI.

  11. Formation of polar ionospheric tongue of ionization during minor geomagnetic disturbed conditions

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Nakamura, Takuji; Liu, Libo; Wang, Wenbin; Balan, Nanan; Nishiyama, Takanori; Hairston, Marc R.; Thomas, E. G.

    2015-08-01

    Previous investigations of ionospheric storm-enhanced density (SED) and tongue of ionization (TOI) focused mostly on the behavior of TOI during intense geomagnetic storms. Little attention has been paid to the spatial and temporal variations of TOI during weak to moderate geomagnetic disturbed conditions. In this paper we investigate the source and development of TOI during a moderate geomagnetic storm on 14 October 2012. Multi-instrumental observations including GPS total electron content (TEC), Defense Meteorological Satellite Program (DMSP) in situ measured total ion concentration and ion drift velocity, SuperDARN measured polar ion convection patterns, and electron density profiles from the Poker Flat Incoherent Scatter Radar (PFISR) have been utilized in the current analysis. GPS TEC maps show salient TOI structures persisting for about 5 h over high latitudes of North America on 14 October 2012 in the later recovery phase of the storm when the magnitudes of IMF By and Bz were less than 5 nT. The PFISR electron density profiles indicate that the extra ionization for TEC enhancements mainly occurred in the topside ionosphere with no obvious changes in the bottomside ionosphere and vertical plasma drifts. Additionally, there were no signatures of penetration electric fields in the equatorial electrojet data and upward ion drifts at high latitudes. At the same time, strong subauroral polarization streams with ion drift speeds exceeding 2.5 km/s carried sunward fluxes and migrated toward lower latitudes for about 5° based on the DMSP cross-track drift measurements. Based on those measurements, we postulate that the combined effects of initial build-up of ionization at midlatitudes through daytime production of ionization and equatorward (or less poleward than normal daytime) neutral wind reducing downward diffusion along the inclined filed lines, and an expanded polar ion convection pattern and its associated horizontal plasma transport are important in the

  12. Effects of geomagnetic activity in the winter thermosphere 2. Magnetically disturbed conditions

    SciTech Connect

    Hagan, M.E. )

    1988-09-01

    The effects of geomagnetic activity on the middle-latitude ionosphere and thermosphere which were monitored by the Millstone Hill incoherent scatter radar during a series of large magnetic substorms during February 7-10, 1986, are presented and discussed. These data are compared with similar measurements from the geomagnetically undisturbed January 1986 period. The effects of ion-neutral frictional heating associated with magnetic substorms are initially quantified by comparative analyses of the ion temperatures from the January and February 1986 experiments. Ion temperature enhancements of 900-1,500K were observed between 30{degree} and 50{degree}N during the most intense substorm. Thermospheric temperature and wind determinations from the two periods are similarly compared. Exospheric temperature enhancements of 200-500K characterize the entire storm period, with larger enhancements during the most disturbed times. Thermospheric temperatures remained elevated well into the recovery period. The accuracy of the Joule heating correction to the temperature determinations for the February experiment is measured against three cases: no neutral motion, neutral motion equal in magnitude and direction to the ion flow, and neutral motion equal in magnitude but opposite in direction to the ion flow. Finally, thermospheric meridional wind field are presented and discussed.

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

    NASA Technical Reports Server (NTRS)

    Stolov, H. L.; Shapiro, R.

    1973-01-01

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

  14. WINDII observations and TIME-GCM simulations of O(1S) polar spirals during geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Shepherd, Gordon G.; Roble, Raymond G.; Cho, Young-Min

    2013-05-01

    daytime O(1S) emission at 557.7 nm observed at 250 km with the Wind Imaging Interferometer (WINDII) is dominantly excited by photoelectron impact on atomic oxygen, so the volume emission rate is normally a measure of the atomic oxygen concentration. Daily polar maps of the 250 km volume emission rate during geomagnetic disturbances display polar spirals extending out of the auroral region and down to the equator. Since the local time is fixed for a given latitude for a single day, the spiral maps form a spatio-temporal pattern in which the longitudinal variations cannot be distinguished from those in universal time. Simulations for 2 January 1993 implemented with the National Center for Atmospheric Research Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) using the equivalent satellite perspective show a remarkably similar spiral pattern. Hourly universal time simulations reveal a rapid equatorward expansion of the spirals during this modest geomagnetic event of Kp = 4.7, which are mirrored in the meridional and vertical winds. Simulations of the electron density show that the emission within the spirals is caused by the recombination of O2+ ions with electrons, and not the atomic oxygen enhancement itself. All of this strongly suggests that the spirals are in fact large-scale Traveling Ionospheric Disturbances (TIDs), and comparisons of the WINDII data made with TID observations reported in the literature, including those made on the same day, support this conclusion. The TIME-GCM simulations suggest that a component of the spirals originates in the lower atmosphere and appears at thermospheric heights.

  15. Analysis of Changes of Cardiological Parameters at Middle Latitude Region in Relation to Geomagnetic Disturbances and Cosmic Ray Variations

    NASA Astrophysics Data System (ADS)

    Papailiou, M.; Dimitrova, S.; Babayev, E. S.; Mavromichalaki, H.

    2010-01-01

    Collaborating scientific groups from Athens (Greece), Baku (Azerbaijan) and Sofia (Bulgaria) have conducted a research work on the possible effects of geomagnetic field disturbances (GMF) and cosmic ray intensity (CRI) variations on human homeostasis, particularly, the cardio-health state. Electrocardiograms (ECGs) of seven functionally healthy persons were digitally registered at the joint Laboratory of Heliobiology located in the Medical Centre INAM, Baku, on working days and Saturdays. Heart rate values, estimated from ECGs, were analysed in relation to daily values of CRI, as measured by the Neutron Monitor of the University of Athens and daily variations of Dst and Ap geomagnetic indices and some significant results had been revealed in previous studies. Researches were continued by study of additional cardiologic parameters estimated from the same ECG data. In this study digital data of RR interval (the time elapsing between two consecutive R waves in the ECG), namely RRminimum, RRmaximum and RRaverage were analyzed taking into consideration different levels of GMF disturbances (estimated through variations of Dst and Ap indices) and cosmic ray activity (through CRI variations). The data refer to the time period 15 July 2006-31 March 2008. Variations of RR intervals show connection to GMF disturbances and CRI variations. The revealed effects are more pronounced for high levels of geomagnetic activity (when geomagnetic storms occur) and large CRI decreases as well as on the days before and after these variations.

  16. Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Willis, Emily M.; Neergaard Parker, Linda

    2014-01-01

    Spacecraft charging of the International Space Station (ISS) is dominated by interaction of the US high voltage solar arrays with the F2-region ionosphere plasma environment. ISS solar array charging is enhanced in a high electron density environment due to the increased thermal electron currents to the edges of the solar cells. High electron temperature environments suppress charging due to formation of barrier potentials on the charged solar cell cover glass that restrict the charging currents to the cell edge [Mandell et al., 2003]. Environments responsible for strong solar array charging are therefore characterized by high electron densities and low electron temperatures. In support of the ISS space environmental effects engineering community, we are working to understand a number of features of solar array charging and to determine how well future charging behavior can be predicted from in-situ plasma density and temperature measurements. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that occur at ISS orbital altitudes (approximately 400 km) over time scales of days, the latitudes over which significant variations occur, and the time periods over which the disturbances persist once they start. This presentation provides examples of mid-latitude electron density and temperature disturbances at altitudes relevant to ISS using data sets and tools developed for our ISS plasma environment study. "Mid-latitude" is defined as the extra-tropical region between approx. 30 degrees to approx. 60 degrees magnetic latitude sampled by ISS over its 51.6 degree inclination orbit. We focus on geomagnetic storm periods because storms are well known drivers for disturbances in the ionospheric plasma environment.

  17. A MU radar-based study of mid-latitude F region response to a geomagnetic disturbance

    SciTech Connect

    Reddy, C.A.; Fukao, S.; Takami, T.; Yamamoto, M.; Tsuda, T.; Nakamura, T.; Kato, S. )

    1990-12-01

    During the night of January 20-21, 1989, ionospheric incoherent scatter power measurements were made with the MU (middle and upper atmosphere) radar at Shigaraki (geographic latitude 34.85 N, longitude 136.10 E; geomagnetic latitude 24.9{degree}, longitude 204.3{degree}). Japan, and the electron density profiles in the 180- to 1,000-km height range were derived at 8-min intervals. The observations showed the presence of three F region disturbances during the night. During the very large first disturbance, which lasted from 2,300 to 0240 LT approximately, the height of maximum electron density N{sub m} increased by 220 km in 2 hours to reach an altitude of 600 km. The other two, smaller disturbances occurred during 0300-0500 LT and 0530-0700 LT approximately. A detailed interpretation of the above F region disturbances is given. Examination of some high- and middle-latitude magnetograms showed the beginning of an intense geomagnetic substorm at auroral latitudes at the start of the first F region disturbance, and a less intense substorm around the starting time of the second F region disturbance. On the basis of this evidence, the first two F region disturbances are interpreted as the result of large vertical drifts of F region ionization due to the substorm-generated east-west electric fields appearing at mid-latitudes. The patterns of h{prime}F variations during this night at five ionospheric stations in Japan support the above interpretation. Additionally, during the second disturbance the possible presence of a wind perturbation due to the equatorward propagation of a wave disturbance, generated probably by the first major substorm, is indicated by the MU radar data and the ionosonde data. The third F region disturbance is attributed to a neutral wind perturbation associated with a gravity wave traveling equatorward, the wave being generated most plausibly by the Joule heating during the first major substorm.

  18. Modelling the disturbance caused by a dc-electrified railway to geomagnetic measurements

    NASA Astrophysics Data System (ADS)

    Pirjola, R.; Newitt, L.; Boteler, D.; Trichtchenko, L.; Fernberg, P.; McKee, L.; Danskin, D.; Jansen van Beek, G.

    2007-08-01

    Magnetic fields created by a dc-electrified railway are a nuisance to the operation of a geomagnetic observatory and also disturb other electromagnetic studies. Theoretical formulas that enable quantitative estimates of the magnetic effect of a dc railway including leakage currents in the ground are presented in this paper. They are illustrated by numerical examples. The validity of the theoretical model was verified by measurements carried out in the vicinity of a nearly north-south railway in Calgary, Canada. The earth structure in that area is approximately layered, which is an assumption included in the theoretical model. The agreement between the measured magnetic fields due to trains and the theoretical values is good. Numerical computations indicate that magnetic fields larger than the maximum allowable noise level (assumed to be about 10 pT) at today's magnetic observatories may extend to distances of tens of kilometres from a railway. We have prepared computer programs based on the theoretical formulas in the MatLab, Octave, FORTRAN and IDL languages, in which the locations (i.e. the latitudes and the longitudes) of the point of observation, of the feeding substations and of the trains, together with the feeding and leakage currents and the heights of the feeding lines, can be given as inputs.

  19. Geomagnetic transmission disturbances and heavy-ion fluences observed in low Earth orbit during the solar energetic particle events of October 1989.

    PubMed

    Boberg, P R; Tylka, A J; Adams, J H; Beahm, L P; Fluckiger, E O; Kleis, T; Kobel, E

    1996-01-01

    The large solar energetic particle (SEP) events and simultaneous large geomagnetic disturbances observed during October 1989 posed a significant, rapidly evolving space radiation hazard. Using data from the GOES-7, NOAA-10, IMP-8 and LDEF satellites, we determined the geomagnetic transmission, heavy ion fluences, mean Fe ionic charge state, and effective radiation hazard observed in low Earth orbit (LEO) for these SEPs. We modeled the geomagnetic transmission by tracing particles through the combination of the internal International Geomagnetic Reference Field (IGRF) and the Tsyganenko (1989) magnetospheric field models, extending the modeling to large geomagnetic disturbances. We used our results to assess the radiation hazard such very large SEP events would pose in the anticipated 52 degrees inclination space station orbit.

  20. Observations from Millstone Hill during the geomagnetic disturbances of March and April 1990

    SciTech Connect

    Buonsanto, M.J.; Foster, J.C.; Sipler, D.P. )

    1992-02-01

    The incoherent scatter radars at Millstone Hill operated continuously during the periods March 16-23 and April 6-12, 1990, providing observations of large-scale ionospheric structure and dynamics over a large portion of eastern North America. Major geomagnetic storms occurred during each of these periods, with deep nighttime ionospheric troughs and large magnetospheric convection electric fields observed equatorward of Millstone. The Millstone observations provide a comprehensive data set detailing storm-induced ionospheric effects over a 35{degree} span of latitude during both of these intervals. At the latitude of Millstone the ionospheric peak height hmF2 rose above 600 km the into trough on March 22 and 23 and reached {approx}500 km at night on April 11 and 12. Increased recombination, apparently due to the strong electric fields, te temperature dependent recombination rate coefficient, and neutral composition changes, greatly depleted the F2 region over a wide latitude range during the day on April 10, 1990. This resulted in an ionosphere dominated by molecular ions, with ionospheric peak heights below 200 km on this day. A number of frictional heating events during the disturbed periods are seen from comparison of ion temperature and velocity measurements. The most intense event took place near 1200 UT on April 10, 1990, when Kp reached 8. At 0100 UT on March 21, line of sight ion velocities in excess of 500 ms{sup {minus}1} were observed at the extreme southern limit of the Millstone steerable radar's field of view (40{degree} apex magnetic latitude at an altitude of 700 km). These could be due to penetration of magnetospheric electric fields or electric fields associated with ring current shielding in the storm-time outer plasmasphere. About an hour later, ion outflow was observed just equatorward of Millstone.

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

    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.

  2. Observed geomagnetic induction effect on Dst-related magnetic observations under different disturbance intensities of the magnetospheric ring current

    NASA Astrophysics Data System (ADS)

    Xu, Dan; Chen, Huaran; Gao, Mengtan

    2015-01-01

    Based on the spherical harmonic expansion of geomagnetic disturbance observed on the mid-latitude surface of the Earth, external and internal field separation is conducted in which the external component is magnetic disturbance caused by the magnetospheric ring current and the internal component is that raised by the correspondingly induced currents within the Earth. The objectives are to evaluate the influences of the induced internal field on the surface magnetic observations and to reveal the response performance of internal geomagnetic induction under different strengths of magnetospheric ring current fluctuations for better understanding of the disturbance storm time ( Dst) index variations. The results show that the ratio of the internal component to surface observation does not remain constant in storm time. During the main phase of the storm, the ratio variation follows the pattern of logarithmic growth with storm evolution up to the top value at the Dst-minimum; then, the ratio slowly decreases in the long recovery phase. Multiple small logarithmic growths are superimposed on the traces of internal ratios, corresponding to temporary ring current intensification during the storm main phase and amplifying the effect of this intensification on surface magnetic observations. With the intensification of magnetospheric storms from the level of (-200 nT, - 100 nT) to (-300 nT, - 200 nT) and (-500 nT, - 300 nT) classified with the Dst-minimum, the top value of the ratio averaged for each storm group in the superposed epoch analysis method increases from the value of 0.295 ± 0.014 to 0.300 ± 0.016 and 0.308 ± 0.015, respectively. It is demonstrated that the geomagnetic induction exceeds the linear relation with the intensification of the external field, which is physically reasonable and coincident with the Faraday's law of induction. Due to the effects of high induction of the oceans and lateral heterogeneity of electric conductivity distribution in the upper

  3. Assessment of scintillation proxy maps for a scintillation study during geomagnetically quiet and disturbed conditions over Uganda

    NASA Astrophysics Data System (ADS)

    Amabayo, Emirant B.; Jurua, Edward; Cilliers, Pierre J.

    2017-02-01

    The objective of this paper is demonstrate the validity and usefulness of scintillation proxies derived from IGS data, through its comparison with data from dedicated scintillation monitors and its application to GNSS scintillation patterns. The paper presents scintillation patterns developed by using data from the dedicated scintillation monitors of the scintillation network decision aid (SCINDA) network, and proxy maps derived from IGS GPS data for 2011 and 2012 over low latitude stations in Uganda. The amplitude and phase scintillation indicies (S4 and σΦ) were obtained from the Novatel GSV4004B ionospheric scintillation and total electron content (TEC) monitor managed by SCINDA at Makerere (0.340N, 32.570E). The corresponding IGS GPS proxy data were obtained from the receivers at Entebbe (0.040N, 32.440E) and Mbarara (0.600S, 30.740E). The derived amplitude (S4p) and phase (sDPR) scintillation proxy maps were compared with maps of S4 and σΦ during geomagnetic storms (moderate and strong) and geomagnetically quiet conditions. The scintillation patterns using S4 and σΦ and their respective proxies revealed similar diurnal and seasonal patterns of strong scintillation occurrence. The peaks of scintillation occurrence with mean values in the range 0.3 < (S4p , sDPR) ≤ 0.6 were observed during nighttime (17:00-22:00 UT) and in the months of March-April and September-October. The results also indicate that high level scintillations occur during geomagnetically disturbed (moderate and strong) and quiet conditions over the Ugandan region. The results show that SCINDA and IGS based scintillation patterns reveal the same nighttime and seasonal occurrence of irregularities over Uganda irrespective of the geomagnetic conditions. Therefore, the amplitude and phase scintillation proxies presented here can be used to fill gaps in low-latitude data where there are no data available from dedicated scintillation receivers, irrespective of the geomagnetic conditions.

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

    NASA Astrophysics Data System (ADS)

    Iipponen, Juho; Laitinen, Tiera

    2015-07-01

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

  5. Comment on the existence of a long range correlation in the geomagnetic disturbance storm time (Dst) index

    NASA Astrophysics Data System (ADS)

    Lacasa, Lucas

    2012-01-01

    Very recently (Banerjee et al. in Astrophys. Space, doi:10.1007/s10509-011-0836-1, 2011) the statistics of geomagnetic Disturbance storm (Dst) index have been addressed, and the conclusion from this analysis suggests that the underlying dynamical process can be modeled as a fractional Brownian motion with persistent long-range correlations. In this comment we expose several misconceptions and flaws in the statistical analysis of that work. On the basis of these arguments, the former conclusion should be revisited.

  6. Analysis of Geomagnetic Disturbances and Cosmic Ray Intensity Variations in Relation to Medical Data from Rome

    NASA Astrophysics Data System (ADS)

    Giannaropoulou, E.; Papailiou, M.; Mavromichalaki, H.; Tsipis, A.

    2010-07-01

    Over the last few years many studies have been conducted concerning the possible influence of geomagnetic and solar activity and cosmic ray activity on human physiological state and in particular on human cardio - health state. As it is shown the human organism is sensitive to environmental changes and reacts to them through a series of variations of its physiological parameters such as heart rate, arterial systolic and diastolic blood pressure, etc. In this paper daily mean values of heart rate, as they were registered for a group of 2.028 volunteers during medical examinations in the Polyclinico Tor Vergata, Rome, Italy are analyzed in relation to daily cosmic ray intensity variations, as measured by the Neutron Monitor of the University of Athens and daily variations of the geomagnetic indices Dst, Ap and Kp. The results from this study show that geomagnetic activity changes and cosmic rays intensity variations may regulate the human homeostasis.

  7. Response of the H-geocorona to geomagnetic disturbances studied by TWINS Lyman-alpha data

    NASA Astrophysics Data System (ADS)

    Zoennchen, Jochen; Nass, Uwe; Fahr, Hans

    2016-04-01

    We have studied the variation of the exospheric H-density distribution during two geomagnetic storms of different strength in terms of their Dst-index values. This analysis is based on continuously monitored Lyman-alpha data observed by the TWINS1/2-LAD instruments. Since solar Lyman-alpha radiation is resonantly backscattered from geocoronal neutral hydrogen (H), the resulting resonance glow intensity in the optically thin regime is proportional to H-column density along the line of sight (LOS). We quantify the amplitude of the H-density's response to geomagnetic activity for different (observed) angular regions and radial Earth-distances. Interestingly the H-exosphere responded with a comparable density increase to both storms of different strength. Careful analysis of the geomagnetic H-density effect indicates that the temporal density response is well correlated with the Kp-index daily sum, but not with the Dst-index in case of the two analysed storms.

  8. Variations of total electron content during geomagnetic disturbances: A model/observation comparison

    NASA Technical Reports Server (NTRS)

    Roble, G. Lu X. Pi A. D. Richmond R. G.

    1997-01-01

    This paper studies the ionospheric response to major geomagnetic storm of October 18-19, 1995, using the thermosphere-ionosphere electrodynamic general circulation model (TIE-GCM) simulations and the global ionospheric maps (GIM) of total electron content (TEC) observations from the Global Positioning System (GPS) worldwide network.

  9. Infradian biorhythms of mitotic activity esophageal epithelium in male Wistar rats.

    PubMed

    Diatroptov, M E; Makarova, O V

    2015-01-01

    Infradian rhythms of esophageal epithelium mitotic activity were studied in male Wistar rats of two age groups: 35-45 days (prepubertal) and 3-4 months (adults). Studies of the time course of esophageal epithelium mitotic indexes in adult males showed 4- and 12-day biorhythms, while prepubertal rats exhibited only 4-day infradian biorhythms of this parameter. Studies of the mitotic activity over long periods (3 years) showed 4.058- and 12.175-day periodicity of infradian biorhythms for this parameter, presumably due to external exposures synchronizing the biorhythms. Studies of the mean daily values of the Bz component of interplanetary magnetic field during the period of our research (2012-2013) showed rhythmicities analogous to changes in the mitotic activity of the epithelium. The minimum mitotic indexes were detected on the days of the most pronounced negative values of the interplanetary magnetic field Bz component.

  10. Cetacean beachings correlate with geomagnetic disturbances in Earth's magnetosphere: an example of how astronomical changes impact the future of life

    NASA Astrophysics Data System (ADS)

    Ferrari, Thomas E.

    2017-04-01

    The beaching and stranding of whales and dolphins around the world has been mystifying scientists for centuries. Although many theories have been proposed, few are substantiated by unequivocal statistical evidence. Advances in the field of animal magnetoreception have established that many organisms, including cetaceans, have an internal `compass,' which they use for orientation when traveling long distances. Astrobiology involves not only the origin and distribution of life in the universe, but also the scientific study of how extraterrestrial conditions affect evolution of life on planet Earth. The focus of this study is how cetacean life is influenced by disturbances in its environment that originate from an astrological phenomenon - in the present study that involves solar flares and cetacean beachings. Solar storms are caused by major coronal eruptions on the Sun. Upon reaching Earth, they cause disturbances in Earth's normally stable magnetosphere. Unable to follow an accurate magnetic bearing under such circumstances, cetaceans lose their compass reading while travelling and, depending on their juxtaposition and nearness to land, eventually beach themselves. (1) This hypothesis was supported by six separate, independent surveys of beachings: (A) in the Mediterranean Sea, (B) the northern Gulf of Mexico, (C) the east and (D) west coasts of the USA and two surveys (E and F) from around the world. When the six surveys were pooled (1614 strandings), a highly significant correlation (R 2 = 0.981) of when strandings occurred with when major geomagnetic disturbances in Earth's magnetosphere occurred was consistent with this hypothesis. (2) Whale and dolphin strandings in the northern Gulf of Mexico and the east coast of the USA were correlated (R 2 = 0.919, R 2 = 0.924) with the number of days before and after a geomagnetic storm. (3) Yearly strandings were correlated with annual geomagnetic storm days. (4) Annual beachings of cetaceans from 1998 to 2012 were

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

    USGS Publications Warehouse

    Gannon, J.L.

    2012-01-01

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

  12. Solar large-scale positive polarity magnetic fields and geomagnetic disturbances

    NASA Technical Reports Server (NTRS)

    Bumba, V.

    1972-01-01

    Unlike the negative polarity solar magnetic field large-scale regular features that correlate with enhanced solar activity regions, the positive polarity regular formations formed in the weak and old background magnetic fields seem to correlate well with geomagnetically enhanced periods of time (shifted for 4 days), which means that they seem to be the source of the quiet solar wind. This behavior of the large intervals of heliographic longitude with prevailing positive polarity fields may be followed to the end of the 18th cycle, during the declining part of the 19th cycle, and during the first half of the present 20th cycle of solar activity.

  13. Space Weather, Geomagnetic Disturbances and Impact on the High-Voltage Transmission Systems

    NASA Technical Reports Server (NTRS)

    Pullkkinen, A.

    2011-01-01

    Geomagnetically induced currents (GIC) affecting the performance of high-voltage power transmission systems are one of the most significant hazards space weather poses on the operability of critical US infrastructure. The severity of the threat was emphasized, for example, in two recent reports: the National Research Council (NRC) report "Severe Space Weather Events--Understanding Societal and Economic Impacts: A Workshop Report" and the North American Electric Reliability Corporation (NERC) report "HighImpact, Low-Frequency Event Risk to the North American Bulk Power System." The NRC and NERC reports demonstrated the important national security dimension of space weather and GIC and called for comprehensive actions to forecast and mitigate the hazard. In this paper we will give a brief overview of space weather storms and accompanying geomagnetic storm events that lead to GIC. We will also review the fundamental principles of how GIC can impact the power transmission systems. Space weather has been a subject of great scientific advances that have changed the wonder of the past to a quantitative field of physics with true predictive power of today. NASA's Solar Shield system aimed at forecasting of GIC in the North American high-voltage power transmission system can be considered as one of the ultimate fruits of those advances. We will review the fundamental principles of the Solar Shield system and provide our view of the way forward in the science of GIC.

  14. STATISTICAL STUDY OF STRONG AND EXTREME GEOMAGNETIC DISTURBANCES AND SOLAR CYCLE CHARACTERISTICS

    SciTech Connect

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

    2015-06-20

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

  15. Statistical study of strong and extreme geomagnetic disturbances and solar cycle characteristics

    NASA Astrophysics Data System (ADS)

    Kilpua, Emilia; Nigul, Olspert; Grigorievskiy, Alexander; Käpylä, Maarit; Tanskanen, Eija; Kataoka, Ryuho; Miyahara, Hiroko; Pelt, Jaan; Ying, Liu

    2016-04-01

    Extreme space weather storms are low-probability, but high-consequence events that may have a significant impact on the modern technological infrastructure in space and on ground. We present here the results on the correlation analysis between the occurrence of extreme geomagnetic storms and solar cycle characteristics using an extensive geomagnetic index AA data set spanning over 150 years (13 solar cycles) complemented by the Kakioka magnetometer recordings. Our results show that the correlation between the storm occurrence and the strength of solar cycle decreases from a clear positive correlation with increasing storm magnitude towards a negligible relationship. Hence, also the calmer Sun can launch super-storms. Examples of such events are the Carrington storm in 1859 and the July 2012 CME that impacted the STEREO-A spacecraft, both of which occurred during relatively weak solar cycles. Our results further suggest that while weaker storms occur most frequently in the declining phase the most extreme storms have a tendency to occur near solar maximum. We also discuss the implications of our findings for the connection between the extreme solar eruptions and multi-scale solar dynamo generated magnetic fields.

  16. The cosmic ray differential diurnal variation dependences on the zenith angle and the geomagnetic disturbance

    NASA Technical Reports Server (NTRS)

    Kavlakov, S.; Georgiev, L.

    1985-01-01

    Simultaneous and continuous muon measurements in two opposite azimuthal directions under equal zenith angles demonstrated the importance of this method for cosmic ray diurnal variation investigations. Lately these measurements were extended by means of improved telescopes. The obtained cosmic ray diurnal variations were presented as intensity differential curves. Theoretical investigations connected the properties of these curves with some interplanetary spece parameters. The harmonics of these curves were interpreted physically. Some order difference curves were introduced. In earlier works some dependences between the parameters characterizing the first and the second harmonics of the differential intensity curves and the geomagnetic activity were found. Then all measurements were carried out under only one zenith angle. The results of investigations of similar dependences using data of simultaneous measurements under three different zenith angles are presented.

  17. Gravity anomalies without geomagnetic disturbances interfere with pigeon homing--a GPS tracking study.

    PubMed

    Blaser, Nicole; Guskov, Sergei I; Entin, Vladimir A; Wolfer, David P; Kanevskyi, Valeryi A; Lipp, Hans-Peter

    2014-11-15

    The gravity vector theory postulates that birds determine their position to set a home course by comparing the memorized gravity vector at the home loft with the local gravity vector at the release site, and that they should adjust their flight course to the gravity anomalies encountered. As gravity anomalies are often intermingled with geomagnetic anomalies, we released experienced pigeons from the center of a strong circular gravity anomaly (25 km diameter) not associated with magnetic anomalies and from a geophysical control site, equidistant from the home loft (91 km). After crossing the border zone of the anomaly--expected to be most critical for pigeon navigation--they dispersed significantly more than control birds, except for those having met a gravity anomaly en route. These data increase the credibility of the gravity vector hypothesis.

  18. Geomagnetic disturbance intensity dependence on the universal timing of the storm peak

    NASA Astrophysics Data System (ADS)

    Katus, R. M.; Liemohn, M. W.; Keesee, A. M.; Immel, T. J.; Ilie, R.; Welling, D. T.; Ganushkina, N. Yu.; Perlongo, N. J.; Ridley, A. J.

    2016-08-01

    The role of universal time (UT) dependence on storm time development has remained an unresolved question in geospace research. This study presents new insight into storm progression in terms of the UT of the storm peak. We present a superposed epoch analysis of solar wind drivers and geomagnetic index responses during magnetic storms, categorized as a function of UT of the storm peak, to investigate the dependency of storm intensity on UT. Storms with Dst minimum less than -100 nT were identified in the 1970-2012 era (305 events), covering four solar cycles. The storms were classified into six groups based on the UT of the minimum Dst (40 to 61 events per bin) then each grouping was superposed on a timeline that aligns the time of the minimum Dst. Fifteen different quantities were considered: seven solar wind parameters and eight activity indices derived from ground-based magnetometer data. Statistical analyses of the superposed means against each other (between the different UT groupings) were conducted to determine the mathematical significance of similarities and differences in the time series plots. It was found that the solar wind parameters have no significant difference between the UT groupings, as expected. The geomagnetic activity indices, however, all show statistically significant differences with UT during the main phase and/or early recovery phase. Specifically, the 02:00 UT groupings are stronger storms than those in the other UT bins. That is, storms are stronger when the Asian sector is on the nightside (American sector on the dayside) during the main phase.

  19. Neutral winds and thermosphere/ionosphere coupling and energetics during the geomagnetic disturbances of March 6-10, 1989

    SciTech Connect

    Buonsanto, M.J.; Foster, J.C.; Galasso, A.D.; Sipler, D.P.; Holt, J.M. )

    1990-12-01

    Observations of electron density made using the fully steerable 46-m-diameter antenna at Millstone Hill have been used to derive the peak electron density (NmF2) and the peak height of the F2 region (hmF2) as a function of latitude during the March 6-10, 1989, period. This period was characterized by varying levels of geomagnetic activity, with a magnetic storm commencing near 1,800 UT on March 8. The radar data set presented for this period provides a detailed example of the mid-latitude ionospheric response to geomagnetic disturbances. The derived hmF2 values are combined with measurements of electric field-induced ion drifts and the MSIS-86 model to estimate the meridional neutral winds at thermospheric heights over the geodetic latitude range 30{degree} to 56 N. Strong postmidnight surges in the neutral wind were observed on March 7, 9, and 10 which reached well equatorward of Millstone Hill. The nighttime electron density trough was above Millstone Hill during the disturbances and hmF2 exceeded 500 km in the trough on March 7 and 9. A dusk enhancement in NmF2 followed the magnetic storm commencement on March 8. This is associated with a large increase in westward ion velocity due to the equatorward penetration of magnetospheric electric fields. Large daytime decreases in NmF2, apparently due to a neutral composition disturbance zone, were observed on March 9 and 10, with a sharp gradient on March 9, and a stronger equatorward penetration of the NmF2 decreases on March 10. The Joule heating as a function of latitude is estimated for March 7 and March 9 from calculations of height-integrated Pedersen conductivity and incoherent scatter electric field measurements. In spite of considerably more Joule heating input at high latitudes on March 9, the postmidnight surge is stronger on March 7. This is explained by a combination of Coriolis and ion drag effects.

  20. Geomagnetic Dependence of Medium Scale Traveling Ionospheric Disturbances (MSTIDs) Observed by Mid- and High- Latitude SuperDARN Radars

    NASA Astrophysics Data System (ADS)

    Frissell, N. A.; Baker, J. B.; Ruohoniemi, J.; Miller, E.; West, M.; Bristow, W. A.

    2013-12-01

    Medium Scale Traveling Ionospheric Disturbances (MSTIDs) are wave-like perturbations of the F-region ionosphere with horizontal wavelengths on the order of 100-250 km and periods between ~15 - 60 min. They are generally thought to be the ionospheric manifestation of Atmospheric Gravity Waves (AGWs). High-latitude MSTIDs have been studied using SuperDARN radars for many years, and have typically been attributed to auroral sources propagated by the Earth Reflected Wave (ERW) mode. Tropospheric sources and earthquakes are also known to be sources of MSTIDs. The goal of this study is to see if high- and mid- latitude MSTIDs share the same source region. Observations of MSTIDs using both mid- and high- latitude SuperDARN radars are presented. A case study using MSTIDs observed at the high latitude Goose Bay Radar (GBR) and the midlatitude Blackstone Radar (BKS) suggest that the auroral source is more likely for GBR than for BKS. BKS radar data from June 2010 - June 2011 were searched for signatures of MSTIDs. Statistics of propagation direction and wavelength for each event are used to suggest MSTID sources. Results show that MSTIDs are observed at BKS primarily in the fall/winter months, which is consistent with previously published results for high latitude stations. Distributions of MSTID occurrence organized by geomagnetic parameters Kp, SYM-H, and AE are presented to investigate MSTID dependence on geomagnetic activity at BKS. No correlation is found between these parameters and midlatitude MSTID occurrence, which suggests that high- and mid-latitude MSTIDs have different sources.

  1. Decay of the Dst field of geomagnetic disturbance after substorm onset and its implication to storm-substorm relation

    NASA Astrophysics Data System (ADS)

    Iyemori, T.; Rao, D. R. K.

    1996-06-01

    In order to investigate the causal relationship between magnetic storms and substorms, variations of the mid-latitude geomagnetic indices, ASY (asymmetric part) and SYM (symmetric part), at substorm onsets are examined. Substorm onsets are defined by three different phenomena; (1) a rapid increase in the mid-latitude asymmetric-disturbance indices, ASY-D and ASY-H, with a shape of so-called `mid-latitude positive bay\\'; (2) a sharp decrease in the AL index; (3) an onset of Pi2 geomagnetic pulsation. The positive bays are selected using eye inspection and a pattern-matching technique. The 1-min-resolution SYM-H index, which is essentially the same as the hourly Dst index except in terms of the time resolution, does not show any statistically significant development after the onset of substorms; it tends to decay after the onset rather than to develop. It is suggested by a simple model calculation that the decay of the magnetospheric tail current after substorm onset is responsible for the decay of the Dst field. The relation between the IMF southward turning and the development of the Dst field is re-examined. The results support the idea that the geomagnetic storms and substorms are independent processes; that is, the ring-current development is not the result of the frequent occurrence of substorms, but that of enhanced convection caused by the large southward IMF. A substorm is the process of energy dissipation in the magnetosphere, and its contribution to the storm-time ring-current formation seems to be negligible. The decay of the Dst field after a substorm onset is explained by a magnetospheric energy theorem. Acknowledgements. This study is supported in part by the Ministry of Education, Science, Sports, and Culture in Japan, under a Grant-in-Aid for Scientific Research (Category B). Topical Editor D. Alcaydé thanks M. Lockwood and N. J. Fox for their help in evaluating this paper.-> Correspondence to: Y. Kamide->

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

    USGS Publications Warehouse

    Gannon, Jennifer

    2012-01-01

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

  3. 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)

    Pietrella, M.

    2012-02-01

    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(τ)), for each observatory. Under the assumption that the ionospheric disturbance index ln(foF2/foF2QT) is correlated to the integrated geomagnetic disturbance index ap(τ), 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

  4. If ionospheric and geomagnetic disturbances observed before strong earthquakes may result from simultaneous impact of space weather on all geospheres including solid earth

    NASA Astrophysics Data System (ADS)

    Khachikyan, Galina

    2016-07-01

    It is revealed in previous decades that ionospheric disturbances precede strong earthquakes, thus, the ionospheric precursors of strong earthquakes are now under developing [Pulinets and Boyarchuk, 2004]. Simultaneously, it is revealed that strong earthquakes may be preceded by geomagnetic disturbances as well, as a result, the geomagnetic variations, for example, in the ULF band, are considered now as precursory signals [Fraser-Smith, 1990, doi/10.1029/GL017i009p01465]. At the same time, there is currently no reliable theory nor for ionospheric or to magnetic precursors of earthquakes. Moreover, several researches have reexamined some of above results and concluded that observed magnetic disturbances before strong earthquakes could be generated by other sources, such as global magnetic activity [e.g. Campbell, 2009, doi/10.1029/2008JA013932], and that ionospheric anomalies can also be an effect of the increase of the global magnetic activity [e. g. Masci and Thomas, 2015, doi:10.1002/2015RS005734]. Taking into account such conclusions, one may suggest that the observed ionospheric and geomagnetic disturbances before strong earthquakes might be due to simultaneous influence of a space weather on the complicated surrounding system including the solid earth. This report presents some statistical results to prove such suggestion. In particular, it is shown [Khachikyan et al., 2012, doi:10.4236/ijg.2012.35109] that maximal possible earthquake magnitude (seismic potential) can be determined, in first approximation, on the base of geomagnetic Z-component measured in the Geocentric Solar Magnetosphere (GSM) coordinate system, in which the space weather impact on the earth's environment, due to reconnection of the solar wind magnetic field with the earth's magnetic field, is more ordered.

  5. The latitudinal variation of geoelectromagnetic disturbances during large (Dst≤-100 nT) geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Woodroffe, J. R.; Morley, S. K.; Jordanova, V. K.; Henderson, M. G.; Cowee, M. M.; Gjerloev, J. G.

    2016-09-01

    Geoelectromagnetic disturbances (GMDs) are an important consequence of space weather that can directly impact many types of terrestrial infrastructure. In this paper, we analyze 30 years of SuperMAG magnetometer data from the range of magnetic latitudes 20°≤λ≤75° to derive characteristic latitudinal profiles for median GMD amplitudes. Based on this data, we obtain a parameterization of these latitudinal profiles of different types of GMDs, providing an analytical fit with Dst-dependent parameters. We also obtain probabilistic estimates for the magnitudes of "100 year" GMDs, finding that Ḃ = 6.9 (3.60-12.9) nT/s should be expected at 45°≤λ < 50°, exceeding the 5 nT/s threshold for dangerous inductive heating.

  6. Latitudinal and longitudinal behavior of the geomagnetic field during a disturbed period: A case study using wavelet techniques

    NASA Astrophysics Data System (ADS)

    Klausner, Virginia; Domingues, Margarete Oliveira; Mendes, Odim; da Costa, Aracy Mendes; Papa, Andres Reinaldo Rodriguez; Gonzalez, Arian Ojeda

    2016-11-01

    Coronal mass ejections are the primary cause of the highly disturbed conditions observed in the magnetosphere. Momentum and energy from the solar wind are transferred to the Earth's magnetosphere mainly via magnetic reconnection which produces open field lines connecting the Earth magnetic field to the solar wind. Magnetospheric currents are coupled to the ionosphere through field-aligned currents. This particular characteristic of the magnetosphere-ionosphere interconnection is discussed here on the basis of the energy transfer from high (auroral currents) to low-latitudes (ring current). The objective of this work is to examine how the conditions during a magnetic storm can affect the global space and time configuration of the ring current, and, how these processes can affect the region of the South Atlantic Magnetic Anomaly. The H- or X-components of the Earth's magnetic field were examined using a set of six magnetometers approximately aligned around the geographic longitude at about 10 °, 140 ° and 295 ° from latitudes of 70 ° N to 70 ° S and aligned throughout the equatorial region, for the event of October 18-22, 1998. The investigation of simultaneous observations of data measured at different locations makes it possible to determine the effects of the magnetosphere-ionosphere coupling, and, it tries to establish some relationships among them. This work also compares the responses of the aligned magnetic observatories to the responses in the South Atlantic Magnetic Anomaly region. The major contribution of this paper is related to the applied methodology of the discrete wavelet transform. The wavelet coefficients are used as a filter to extract the information in high frequencies of the analyzed magnetogram. They also better represent information about the injections of energy and, consequently, the disturbances of the geomagnetic field measured on the ground. As a result, we present a better way to visualize the correlation between the X- or H

  7. Solar wind-magnetosphere interaction during the possible encounter of Comet Halley's tail in 1910 inferred from mid-latitude geomagnetic field disturbances

    NASA Astrophysics Data System (ADS)

    Iyemori, T.; Araki, T.

    Geomagnetic disturbances from the period April to June 1910 are analyzed to detect the possible effects of the Comet Halley on the solar wind-magnetosphere interaction. Data from six midlatitude geomagnetic observatories are used to calculate the longitudinally symmetric (i.e., Dst) and asymmetric fields. An application of a linear prediction filter to separate the solar wind dynamic pressure effect on the disturbances from that of the ring current, suggests that there exists a compressional variation in the Dst on May 18 which is around or slightly earlier than the time of estimated cometary tail encounter. The normal-run magnetogram from Agincourt on the dayside and that from Lu-Kia-Pang on the nightside, also indicate rather strong (i.e., 30-40 nT) compressional variation. The disturbances characteristic to the solar wind-magnetosphere interaction under the southward IMF condition and that of the ring current development are seen during the period. These results suggest that the earth's magnetosphere had been affected by a dense cometary plasma tail with high dynamic pressure, though the solar wind-magnetosphere interaction typically observed under the southward IMF condition had been taking place during the encounter.

  8. Geomagnetic disturbances and pulsations as a high-latitude response to considerable alternating IMF Variations during the magnetic storm recovery phase (Case study: May 30, 2003)

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Features of high-latitude geomagnetic disturbances during the magnetic storm ( Dst min =-144 nT) recovery phase were studied based on the observations on the Scandinavian profile of magnetometers (IMAGE). Certain non-typical effects that occur under the conditions of large positive IMF Bz values (about +20-25 nT) and large negative IMF By values (to-20 nT) were revealed. Thus, an intense (about 400 nT) negative bay in the X component of the magnetic field (the polar electrojet, PE) was observed in the dayside sector at geomagnetic latitudes higher than 70°. As the IMF B y reverses its sign from negative to positive, the bay in the X component was replaced by the bay in the Y component. The possible distribution of the fieldaligned currents of the NBZ system was analyzed based on the CHAMP satellite data. The results were compared with the position of the auroral oval (the OVATION model) and the ion and electron flux observations on the DMSP satellite. Analysis of the particle spectra indicated that these spectra correspond to the auroral oval dayside sector crossings by the satellite, i.e., to the dayside projection of the plasma ring surrounding the Earth. Arguments are presented for the assumption that the discussed dayside electrojet ( PE) is localized near the polar edge of the dayside auroral oval in a the closed magnetosphere. The features of the spectral and spatial dynamics of intense Pc5 geomagnetic pulsations were studied in this time interval. It was established that the spectrum of high-latitude (higher than ~70°) pulsations does not coincide with the spectrum of fluctuations in the solar wind and IMF. It was shown that Pc5 geomagnetic pulsations can be considered as resonance oscillations at latitudes lower than 70° and apparently reflect fluctuations in turbulent sheets adjacent to the magnetopause (the low-latitude boundary layer, a cusp throat) or in a turbulent magnetosheath at higher latitudes.

  9. Effects of Meteorological Variability on the Thermosphere-Ionosphere System during the Moderate Geomagnetic Disturbed January 2013 Period As Simulated By Time-GCM

    NASA Astrophysics Data System (ADS)

    Maute, A. I.; Hagan, M. E.; Richmond, A. D.; Liu, H.; Yudin, V. A.

    2014-12-01

    The ionosphere-thermosphere system is affected by solar and magnetospheric processes and by meteorological variability. Ionospheric observations of total electron content during the current solar cycle have shown that variability associated with meteorological forcing is important during solar minimum, and can have significant ionospheric effects during solar medium to maximum conditions. Numerical models can be used to study the comparative importance of geomagnetic and meterological forcing.This study focuses on the January 2013 Stratospheric Sudden Warming (SSW) period, which is associated with a very disturbed middle atmosphere as well as with moderately disturbed solar geomagntic conditions. We employ the NCAR Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) with a nudging scheme using Whole-Atmosphere-Community-Climate-Model-Extended (WACCM-X)/Goddard Earth Observing System Model, Version 5 (GEOS5) results to simulate the effects of the meteorological and solar wind forcing on the upper atmosphere. The model results are evaluated by comparing with observations e.g., TEC, NmF2, ion drifts. We study the effect of the SSW on the wave spectrum, and the associated changes in the low latitude vertical drifts. These changes are compared to the impact of the moderate geomagnetic forcing on the TI-system during the January 2013 time period by conducting numerical experiments. We will present select highlights from our study and elude to the comparative importance of the forcing from above and below as simulated by the TIME-GCM.

  10. Lack of evidence for meteorological effects on infradian dynamics of testosterone

    NASA Astrophysics Data System (ADS)

    Celec, Peter; Smreková, Lucia; Ostatníková, Daniela; Čabajová, Zlata; Hodosy, Július; Kúdela, Matúš

    2009-09-01

    Climatic factors are known to influence the endocrine system. Previous studies have shown that circannual seasonal variations of testosterone might be partly explained by changes in air temperature. Whether infradian variations are affected by meteorological factors is unknown. To analyze possible effects of meteorological parameters on infradian variations of salivary testosterone levels in both sexes, daily salivary testosterone levels were measured during 1 month in 14 men and 17 women. A correlation analysis between hormonal levels and selected meteorological parameters was performed. The results indicate that high testosterone levels are loosely associated with cold, sunny and dry weather in both sexes. However, only the correlations between testosterone and air temperature (men) and actual cloudiness (women) were statistically significant ( p < 0,05). Although some correlations reached the level of statistical significance, the effects of selected meteorological parameters on salivary testosterone levels remain unclear. Further longer-term studies concentrating on air temperature, cloudiness and average relative humidity in relation to the sex hormone axis are needed.

  11. Evidence of low-latitude daytime large-scale traveling ionospheric disturbances observed by high-frequency multistatic backscatter sounding system during a geomagnetically quiet period

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Zhao, Zhengyu; Yang, Guobin; Chen, Gang; Hu, Yaogai; Zhang, Yuannong

    2012-06-01

    Observations from the high-frequency multistatic backscatter sounding radars on a geomagnetically quiet day (minimum Dst = -14 nT) captured the anti-equatorward propagation of daytime large-scale traveling ionospheric disturbance (LSTID) at the low-latitude regions. The observed LSTID was characterized approximately by a meridional propagation speed of 347 ± 78 m/s and azimuthal angle of -4.7 ± 27.6° (counterclockwise from north), with a period of 76 min and a wavelength of 1583 ± 354 km by means of maximum entropy cross-spectral analysis. Vertical phase velocity was also evaluated to be <˜42 m/s through the Doppler measurements. These results provide evidence that the low-latitude ionosphere can undergo large-scale perturbations even under geomagnetically quiet conditions. We suggest that this observed LSTID could be due to the secondary gravity waves from thermospheric body forces created from the dissipation of primary gravity waves from deep tropospheric convection.

  12. The response of the H geocorona between 3 and 8 Re to geomagnetic disturbances studied using TWINS stereo Lyman-α data

    NASA Astrophysics Data System (ADS)

    Zoennchen, Jochen H.; Nass, Uwe; Fahr, Hans J.; Goldstein, Jerry

    2017-02-01

    Circumterrestrial Lyman-α column brightness observations from 3-8 Earth radii (Re) have been used to study temporal density variations in the exospheric neutral hydrogen as response to geomagnetic disturbances of different strength, i.e., Dst peak values between -26 and -147 nT. The data used were measured by the two Lyman-α detectors (LAD1/2) onboard both TWINS satellites between the solar minimum of 2008 and near the solar maximum of 2013. The solar Lyman-α flux at 121.6 nm is resonantly scattered near line center by exospheric H atoms and measured by the TWINS LADs. Along a line of sight (LOS), the scattered LOS-column intensity is proportional to the LOS H column density, assuming optically thin conditions above 3 Re. In the case of the eight analyzed geomagnetic storms we found a significant increase in the exospheric Lyman-α flux between 9 and 23 % (equal to the same increase in H column density ΔnH) compared to the undisturbed case short before the storm event. Even weak geomagnetic storms (e.g., Dst peak values ≥ -41 nT) under solar minimum conditions show increases up to 23 % of the exospheric H densities. The strong H density increase in the observed outer exosphere is also a sign of an enhanced H escape flux during storms. For the majority of the storms we found an average time shift of about 11 h between the time when the first significant dynamic solar wind pressure peak (pSW) hits the Earth and the time when the exospheric Lyman-α flux variation reaches its maximum. The results show that the (relative) exospheric density reaction of ΔnH have a tendency to decrease with increasing peak values of Dst index or the Kp index daily sum. Nevertheless, a simple linear correlation between ΔnH and these two geomagnetic indices does not seem to exist. In contrast, when recovering from the peak back to the undisturbed case, the Kp index daily sum and the ΔnH essentially show the same temporal recovery.

  13. Lunisolar tidal waves, geomagnetic activity and epilepsy in the light of multivariate coherence.

    PubMed

    Mikulecky, M; Moravcikova, C; Czanner, S

    1996-08-01

    The computed daily values of lunisolar tidal waves, the observed daily values of Ap index, a measure of the planetary geomagnetic activity, and the daily numbers of patients with epileptic attacks for a group of 28 neurology patients between 1987 and 1992 were analyzed by common, multiple and partial cross-spectral analysis to search for relationships between periodicities in these time series. Significant common and multiple coherence between them was found for rhythms with a period length over 3-4 months, in agreement with seasonal variations of all three variables. If, however, the coherence between tides and epilepsy was studied excluding the influence of geomagnetism, two joint infradian periodicities with period lengths of 8.5 and 10.7 days became significant. On the other hand, there were no joint rhythms for geomagnetism and epilepsy when the influence of tidal waves was excluded. The result suggests a more primary role of gravitation, compared with geomagnetism, in the multivariate process studied.

  14. Daytime geomagnetic disturbances at high latitudes during a strong magnetic storm of June 21-23, 2015: The storm initial phase

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    The high-latitude geomagnetic effects of an unusually long initial phase of the largest magnetic storm ( SymH ~-220 nT) in cycle 24 of the solar activity are considered. Three interplanetary shocks characterized by considerable solar wind density jumps (up to 50-60 cm-3) at a low solar wind velocity (350-400 km/s) approached the Earth's magnetosphere during the storm initial phase. The first two dynamic impacts did not result in the development of a magnetic storm, since the IMF Bz remained positive for a long time after these shocks, but they caused daytime polar substorms (magnetic bays) near the boundary between the closed and open magnetosphere. The magnetic field vector diagrams at high latitudes and the behaviour of high-latitude long-period geomagnetic pulsations ( ipcl and vlp) made it possible to specify the dynamics of this boundary position. The spatiotemporal features of daytime polar substorms (the dayside polar electrojet, PE) caused by sudden changes in the solar wind dynamic pressure are discussed in detail, and the singularities of ionospheric convection in the polar cap are considered. It has been shown that the main phase of this two-stage storm started rapidly developing only when the third most intense shock approached the Earth against a background of large negative IMF Bz values (to-39 nT). It was concluded that the dynamics of convective vortices and the related restructing of the field-aligned currents can result in spatiotemporal fluctuations in the closing ionospheric currents that are registered on the Earth's surface as bay-like magnetic disturbances.

  15. Influence of Solar-Geomagnetic Disturbances on SABER Measurements of 4.3 Micrometer Emission and the Retrieval of Kinetic Temperature and Carbon Dioxide

    NASA Technical Reports Server (NTRS)

    Mertens, Christopher J.; Winick, Jeremy R.; Picard, Richard H.; Evans, David S.; Lopez-Puertas, Manuel; Wintersteiner, Peter P.; Xu, Xiaojing; Mlynczak, Martin G.; Russell, James M., III

    2008-01-01

    Thermospheric infrared radiance at 4.3 micrometers is susceptible to the influence of solar-geomagnetic disturbances. Ionization processes followed by ion-neutral chemical reactions lead to vibrationally excited NO(+) (i.e., NO(+)(v)) and subsequent 4.3 micrometer emission in the ionospheric E-region. Large enhancements of nighttime 4.3 m emission were observed by the TIMED/SABER instrument during the April 2002 and October-November 2003 solar storms. Global measurements of infrared 4.3 micrometer emission provide an excellent proxy to observe the nighttime E-region response to auroral dosing and to conduct a detailed study of E-region ion-neutral chemistry and energy transfer mechanisms. Furthermore, we find that photoionization processes followed by ion-neutral reactions during quiescent, daytime conditions increase the NO(+) concentration enough to introduce biases in the TIMED/SABER operational processing of kinetic temperature and CO2 data, with the largest effect at summer solstice. In this paper, we discuss solar storm enhancements of 4.3 micrometer emission observed from SABER and assess the impact of NO(+)(v) 4.3 micrometer emission on quiescent, daytime retrievals of Tk/CO2 from the SABER instrument.

  16. The latitudinal variation of geoelectromagnetic disturbances during large (Dst ≤ ₋100 nT) geomagnetic storms

    DOE PAGES

    Woodroffe, Jesse Richard; Morley, S. K.; Jordanova, V. K.; ...

    2016-09-20

    Geoelectromagnetic disturbances (GMDs) are an important consequence of space weather that can directly impact many types of terrestrial infrastructure. In this paper, we analyze 30 years of SuperMAG magnetometer data from the range of magnetic latitudes 20°≤λ≤75° to derive characteristic latitudinal profiles for median GMD amplitudes. Based on this data, we obtain a parameterization of these latitudinal profiles of different types of GMDs, providing an analytical fit with Dst-dependent parameters. Finally, we also obtain probabilistic estimates for the magnitudes of “100 year” GMDs, finding thatmore » $$\\dot{_B}$$ = 6.9 (3.60–12.9) nT/s should be expected at 45°≤λ< 50°, exceeding the 5 nT/s threshold for dangerous inductive heating.« less

  17. Correlated Measurements of the Disturbances of Geomagnetic Field and Changes of Secondary Particle Fluxes at Aragats-Space Environmental Center (ASEC)

    DTIC Science & Technology

    2010-02-01

    responding to GCR energies ≥ 10 GeV) and Muon Telescopes (MT, responding to GCR energies ≥ 15 GeV) well before the onset of a major geomagnetic storm...S., et al.: Precursors of geomagnetic storms observed by the muon detector network, J. Geophys. Res. 105, 27457-27468, 2000. N. Gopalswamy, S...AMMM Aragats Multidirectional Muon Monitor ANM Aragats Neutron Monitor ASCII American Standard Code for Information Interchange ASEC

  18. Comment on 'Geomagnetic activity associated with earth passage of interplanetary shock disturbances and coronal mass ejections' by J. T. Gosling, D. J. McComas, J. L. Philips, and S. J. Bame

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Gonzalez, Walter D.

    1993-01-01

    It is contended that statistical data do not support the claim of Gosling et al. (1991) to the effect that the initial speed of a solar wind driver gas close to the sun appears to be the most crucial factor in determining if an earthward direct event will be effective in exciting a large geomagnetic disturbance. It is argued that the time intervals are much too large to observe the storm-time B sub Z dependence. Gosling et al. reply that this comment is based on a serious misunderstanding of their conclusions.

  19. Possible influence of solar extreme events and related geomagnetic disturbances on human cardio-vascular state: Results of collaborative Bulgarian-Azerbaijani studies

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.; Mustafa, F. R.; Stoilova, I.; Babayev, E. S.; Kazimov, E. A.

    2009-02-01

    This collaborative study is based on the analysis and comparison of results of coordinated experimental investigations conducted in Bulgaria and Azerbaijan for revealing a possible influence of solar activity changes and related geomagnetic activity variations on the human cardio-vascular state. Arterial blood pressure and heart rate of 86 healthy volunteers were measured on working days during a period of comparatively high solar and geomagnetic activity (2799 measurements in autumn 2001 and spring 2002) in Sofia. Daily experimental investigations of parameters of cardio-vascular health state were performed in Azerbaijan with a permanent group of examined persons. Heart rate and electrocardiograms were digitally registered (in total 1532 records) for seven functionally healthy persons on working days and Saturdays, in the Laboratory of Heliobiology at the Medical Center INAM in Baku, from 15.07.2006 to 13.11.2007. Obtained digital recordings were subjected to medical, statistical and spectral analyses. Special attention was paid to effects of solar extreme events, particularly those of November 2001 and December 2006. The statistical method of the analysis of variance (ANOVA) and post hoc analysis were applied to check the significance of the influence of geomagnetic activity on the cardio-vascular parameters under consideration. Results revealed statistically significant increments for the mean systolic and diastolic blood pressure values of the group with geomagnetic activity increase. Arterial blood pressure values started increasing two days prior to geomagnetic storms and kept their high values up to two days after the storms. Heart rate reaction was ambiguous and not significant for healthy persons examined (for both groups) under conditions with geomagnetic activity changes. It is concluded that heart rate for healthy persons at middle latitudes can be considered as a more stable physiological parameter which is not so sensitive to environmental changes

  20. On extreme geomagnetic storms

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  1. Hazards of geomagnetic storms

    USGS Publications Warehouse

    Herzog, D.C.

    1992-01-01

    Geomagnetic storms are large and sometimes rapid fluctuations in the Earth's magnetic field that are related to disturbances on the Sun's surface. Although it is not widely recognized, these transient magnetic disturbances can be a significant hazard to people and property. Many of us know that the intensity of the auroral lights increases during magnetic storms, but few people realize that these storms can also cause massive power outages, interrupt radio communications and satellite operations, increase corrosion in oil and gas pipelines, and lead to spuriously high rejection rates in the manufacture of sensitive electronic equipment. 

  2. Geomagnetism applications

    USGS Publications Warehouse

    Campbell, Wallace H.

    1995-01-01

    The social uses of geomagnetism include the physics of the space environment, satellite damage, pipeline corrosion, electric power-grid failure, communication interference, global positioning disruption, mineral-resource detection, interpretation of the Earth's formation and structure, navigation, weather, and magnetoreception in organisms. The need for continuing observations of the geomagnetic field, together with careful archiving of these records and mechanisms for dissemination of these data, is emphasized.

  3. Comment on Decay of the Dst Field of Geomagnetic Disturbance After Substorm Onset and its Implication to Storm-Substorm Relation

    NASA Technical Reports Server (NTRS)

    Rostoker, G.; Baumjohann, W.; Gonzalez, W.; Kamide, Y.; Kokubun, S.; McPherron, R. L.; Tsurutani, B. T.

    1996-01-01

    Over the past few years, there has been a considerable revival in the study of geomagnetic storms stimulated by an increasing knowledge of the energetic particles which comprise the ring current. It is only in recent years that the composition of the ring current has been thouroughly explored and the important role of the oxygen component of the near Earth plasma sheet has become recognized.

  4. Geomagnetic effects caused by rocket exhaust jets

    NASA Astrophysics Data System (ADS)

    Lipko, Yuriy; Pashinin, Aleksandr; Khakhinov, Vitaliy; Rahmatulin, Ravil

    2016-09-01

    In the space experiment Radar-Progress, we have made 33 series of measurements of geomagnetic variations during ignitions of engines of Progress cargo spacecraft in low Earth orbit. We used magneto-measuring complexes, installed at observatories of the Institute of Solar-Terrestrial Physics of Siberian Branch of the Russian Academy of Sciences, and magnetotelluric equipment of a mobile complex. We assumed that engine running can cause geomagnetic disturbances in flux tubes crossed by the spacecraft. When analyzing experimental data, we took into account space weather factors: solar wind parameters, total daily mid-latitude geomagnetic activity index Kp, geomagnetic auroral electrojet index AE, global geomagnetic activity. The empirical data we obtained indicate that 18 of the 33 series showed geomagnetic variations in various time ranges.

  5. Ionospheric response to geomagnetic disturbances in the north-eastern region of Asia during the minimum of 23rd cycle of solar activity

    NASA Astrophysics Data System (ADS)

    Kurkin, V. I.; Pirog, O. M.; Polekh, N. M.; Mikhalev, A. V.; Poddelsky, I. N.; Stepanov, A. E.

    2008-12-01

    We present the results of studies of the subauroral and mid-latitude ionosphere variations in the north-eastern region of Asia. We used the data from network of vertical and oblique-incidence sounding ionosondes and optical measurements. Long-term experiments on the radio paths Magadan-Irkutsk and Norilsk-Irkutsk were carried out within the period 2005-2007. Vertical sounding stations operated in standard regime. Observation of airglow near Irkutsk was provided by the zenith photometer that measured intensities of 557.7 and 630.0 nm atomic oxygen emissions. The results may be summarized as follows. (1) Large daytime negative disturbances are observed during the main and recovery phases mainly at high latitudes, whereas the positive disturbances observed during the main phase at mid latitudes. The disturbances changed their sign between Yakutsk and Irkutsk. (2) During the main and recovery storm phases the fall of foF2 associated with the equatorward wall of the main ionospheric trough is observed in the afternoon and evening. (3) Fluctuations of the electron density more intensive at mid latitudes during the storm main phase are observed during all considered periods. They are classed as traveling ionospheric disturbances (TID). Such sharp gradients of electron density are responsible for the strong changes in the characteristics of the radio wave propagation, particularity MOF. (4) A large-scale ionospheric disturbance is noted at the meridional chain of ionosonds in December 2006 as the sharp increase of foF2. It appears in the evening in the minimum of Dst at high latitude and propagate to equator. (5) A maximum of 630 nm emission above Irkutsk corresponds to the foF2 increase. (6) The obtained experimental data on the net of vertical and oblique-incidence sounding with high time resolution show that such net is the effective facility to study the conditions of the radio wave propagation and can be used for the diagnostic of the ionosphere.

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

    NASA Astrophysics Data System (ADS)

    Michelis, Paola De; Consolini, Giuseppe

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  8. Geomagnetically Induced Currents, a space weather hazard. Case study - Europe under intense geomagnetic storms of the solar cycle 23

    NASA Astrophysics Data System (ADS)

    Dobrica, V.; Demetrescu, Cr.; Stefan, C.; Greculeasa, R.

    2016-05-01

    The interaction of the solar wind and heliospheric magnetic field with the magnetosphere and ionosphere results in variations of the geomagnetic field that induce hazardous electric currents in grounded technological systems (electric power and hydrocarbon transportation networks), the so-called geomagnetically induced currents (GICs). In order to evaluate the hazard induced on the European continent, we present a study of the surface electric field induced by 16 intense (Dst < -150 nT) geomagnetic storms, based on the analysis of the geomagnetic records from the European network of observatories, study that tend to solve the geophysical part of the problem. The evolution during storm development and the sources of the disturbance field are explored in case of the largest geomagnetic storm in the cycle 23 (Dst = -422 nT, November 20-21, 2003), and the geographical distribution of the maximum induced surface geoelectric field over Europe by the 16 storms considered in the study is presented. As source proxies, the Dst geomagnetic index, showing the disturbed field produced by the magnetospheric ring current at the geomagnetic equator, the AL geomagnetic index, showing the disturbed field produced by the ionospheric electrojet at auroral latitude, and the PC geomagnetic index, showing the disturbed field produced by the polar cap current, were examined.

  9. The latitudinal variation of geoelectromagnetic disturbances during large (Dst ≤ ₋100 nT) geomagnetic storms

    SciTech Connect

    Woodroffe, Jesse Richard; Morley, S. K.; Jordanova, V. K.; Henderson, M. G.; Cowee, M. M.; Gjerloev, J. G.

    2016-09-20

    Geoelectromagnetic disturbances (GMDs) are an important consequence of space weather that can directly impact many types of terrestrial infrastructure. In this paper, we analyze 30 years of SuperMAG magnetometer data from the range of magnetic latitudes 20°≤λ≤75° to derive characteristic latitudinal profiles for median GMD amplitudes. Based on this data, we obtain a parameterization of these latitudinal profiles of different types of GMDs, providing an analytical fit with Dst-dependent parameters. Finally, we also obtain probabilistic estimates for the magnitudes of “100 year” GMDs, finding that $\\dot{_B}$ = 6.9 (3.60–12.9) nT/s should be expected at 45°≤λ< 50°, exceeding the 5 nT/s threshold for dangerous inductive heating.

  10. A sensitive geomagnetic activity index for space weather operation

    NASA Astrophysics Data System (ADS)

    Du, D.; Xu, W. Y.; Zhao, M. X.; Chen, B.; Lu, J. Y.; Yang, G. L.

    2010-12-01

    There is an ongoing demand for real-time geomagnetic indices in space services. The traditional 3 h K index and K-derived planetary indices cannot issue alters promptly during large storms, and the 3 h interval is much larger than the time scales of ionospheric responses. To overcome these difficulties, we define a new consecutive and linear geomagnetic activity index, the range of hourly H component index (rH) with 1 min resolution, and develop a local rH index nowcast system for space weather operation, which can issue geomagnetic storm alerts quickly. We also derive Kp/Ap indices conveniently from a single station data to describe the global geomagnetic activity. Then we make a statistic comparison between rH and other definite index values during storm and find that rH is sensitive to the geomagnetic disturbance and can reflect the geomagnetic activity more delicately.

  11. Large Geomagnetic Storms: Introduction to Special Section

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Tiwari, Bhupendra Kumar

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

  13. Extreme Geomagnetic Storms - 1868 - 2010

    NASA Astrophysics Data System (ADS)

    Vennerstrom, S.; Lefevre, L.; Dumbović, M.; Crosby, N.; Malandraki, O.; Patsou, I.; Clette, F.; Veronig, A.; Vršnak, B.; Leer, K.; Moretto, T.

    2016-05-01

    We present the first large statistical study of extreme geomagnetic storms based on historical data from the time period 1868 - 2010. This article is the first of two companion papers. Here we describe how the storms were selected and focus on their near-Earth characteristics. The second article presents our investigation of the corresponding solar events and their characteristics. The storms were selected based on their intensity in the aa index, which constitutes the longest existing continuous series of geomagnetic activity. They are analyzed statistically in the context of more well-known geomagnetic indices, such as the Kp and Dcx/Dst index. This reveals that neither Kp nor Dcx/Dst provide a comprehensive geomagnetic measure of the extreme storms. We rank the storms by including long series of single magnetic observatory data. The top storms on the rank list are the New York Railroad storm occurring in May 1921 and the Quebec storm from March 1989. We identify key characteristics of the storms by combining several different available data sources, lists of storm sudden commencements (SSCs) signifying occurrence of interplanetary shocks, solar wind in-situ measurements, neutron monitor data, and associated identifications of Forbush decreases as well as satellite measurements of energetic proton fluxes in the near-Earth space environment. From this we find, among other results, that the extreme storms are very strongly correlated with the occurrence of interplanetary shocks (91 - 100 %), Forbush decreases (100 %), and energetic solar proton events (70 %). A quantitative comparison of these associations relative to less intense storms is also presented. Most notably, we find that most often the extreme storms are characterized by a complexity that is associated with multiple, often interacting, solar wind disturbances and that they frequently occur when the geomagnetic activity is already elevated. We also investigate the semiannual variation in storm occurrence

  14. Local geomagnetic indices and their role in space weather

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    The analysis of local geomagnetic disturbances (specific longitude and latitude) have recently proved to play an important role in space weather research. Localized strong (high intensity) and impulsive (fast developed and fast recovered) geomagnetic disturbances are typically recorded at high latitudes and commonly related to field-aligned currents. These type of disturbances are also recorded, less frequently, at mid and low latitudes, representing an important hazard for technology. In order to obtain geomagnetic disturbances (geomagnetic index) from the records at a certain observatory, a baseline has to be removed. The baseline is usually determined taking into account geomagnetic secular variation and solar quiet time. At mid-latitudes the shape of the daily solar quiet component presents a strong day-to-day variability difficult to predict. In this work we present a new technique capable to determine the baseline at mid-latitudes which allows us to obtain a high resolution local geomagnetic index with the highest accuracy ever obtained at mid-latitudes.

  15. Geomagnetic and atmospheric effects

    NASA Astrophysics Data System (ADS)

    Stoker, P. H.

    1983-08-01

    Geomagnetic and atmospheric processes affecting cosmic-ray earthbound spectrometry are analyzed. The topics discussed include: cutoff rigidities and asymptotic directions; cosmic ray secondaries in the atmosphere and magnetosphere; neutron counters without lead and neutron monitors; and coupling coefficients/yield functions and response functions of cosmic ray detectors. Theoretical simulations of the atmosphere and geomagnetism are presented, taking into account such factors as geomagnetic ring currents and meteorological effects. Diagrams and cutoff rigidity contours are included.

  16. Assessment of extreme values in geomagnetic and geoelectric field variations for Canada

    NASA Astrophysics Data System (ADS)

    Nikitina, L.; Trichtchenko, L.; Boteler, D. H.

    2016-07-01

    Disturbances of the geomagnetic field produced by space weather events can have an impact on power systems and other critical infrastructure. To mitigate these risks it is important to determine the extreme values of geomagnetic activity that can occur. More than 40 years of 1 min magnetic data recorded at 13 Canadian geomagnetic observatories have been analyzed to evaluate extreme levels in geomagnetic and geoelectric activities in different locations of Canada. The hourly ranges of geomagnetic field variations and hourly maximum in rate of change of the magnetic variations have been used as measures of geomagnetic activity. Geoelectric activity is estimated by the hourly peak amplitude of the geoelectric fields calculated with the use of Earth resistivity models specified for different locations in Canada. A generalized extreme value distribution was applied to geomagnetic and geoelectric indices to evaluate extreme geomagnetic and geoelectric disturbances, which could happen once per 50 and once per 100 years with 99% confidence interval. Influence of geomagnetic latitude and Earth resistivity models on the results for the extreme geomagnetic and geoelectric activity is discussed. The extreme values provide criteria for assessing the vulnerability of power systems and other technology to geomagnetic activity for design or mitigation purposes.

  17. Geomagnetism-Paleomagnetism Committee

    NASA Astrophysics Data System (ADS)

    Banerjee, Subir K.

    I n response to strong member concerns about the future of geomagnetism, Neil D. Opdyke, President of the Geomagnetism and Paleomagnetism Section, has appointed an ad hoc Committee for the Future of Geomagnetism and Paleomagnetism consisting of Subir K. Banerjee (chair; University of Minnesota, Minneapolis), Joseph Cain (U.S. Geological Survey, Denver, Colo.) and Rob Van der Voo (University of Michigan, Ann Arbor). The committee seeks, from the membership at large, perceptions of future directions of research, help in identifying a few expanding research areas that show a promise of delivering significant results in the next 5 to 10 years, and guidance in generating a strategy to bring these about.

  18. Geomagnetic excitation of nutation

    NASA Astrophysics Data System (ADS)

    Ron, C.; Vondrák, J.

    2015-08-01

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

  19. Tsunami related to solar and geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2016-04-01

    ascertained by authors from 2012, have confirmed that the four strongest earthquakes (and then the four tsunami) were preceded by a clear increase of the solar wind proton density which subsequently generated perturbation of the Earth's geomagnetic field. The temporal characteristics of the proton increases and geomagnetic disturbances that preceded the four tsunami have a clear predictive significance especially in the face of recent studies on Seismic Solar Precursors (SSPs), on Interplanetary Seismic Precursors (ISPs) and on Seismic Geomagnetic Precursors (SGPs) presented by the authors in the last two years.

  20. Comparison of outliers and novelty detection to identify ionospheric TEC irregularities during geomagnetic storm and substorm

    NASA Astrophysics Data System (ADS)

    Pattisahusiwa, Asis; Houw Liong, The; Purqon, Acep

    2016-08-01

    In this study, we compare two learning mechanisms: outliers and novelty detection in order to detect ionospheric TEC disturbance by November 2004 geomagnetic storm and January 2005 substorm. The mechanisms are applied by using v-SVR learning algorithm which is a regression version of SVM. Our results show that both mechanisms are quiet accurate in learning TEC data. However, novelty detection is more accurate than outliers detection in extracting anomalies related to geomagnetic events. The detected anomalies by outliers detection are mostly related to trend of data, while novelty detection are associated to geomagnetic events. Novelty detection also shows evidence of LSTID during geomagnetic events.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  2. Response of the high-latitude thermosphere to geomagnetic activity

    SciTech Connect

    Rees, D.

    1985-01-01

    Fuller-Rowell and Rees (1980) and Roble et al. (1982) have developed three-dimensional, time-dependent models which simulate the structure and dynamics of the thermosphere with considerable realism. These models are particularly useful for the evaluation of the individual contributions of the many distinct elements of the geomagnetic forcing of the polar thermosphere. A description is given of simulations of the steady-state structure and dynamics of the thermosphere for a level of moderately high solar activity, at the December and June solstices, and for moderately quiet and rather disturbed geomagnetic conditions. In the present paper, the simulations are used for reference purposes. Attention is given to time-dependent simulations of the thermospheric response to large geomagnetic disturbances. 24 references.

  3. New forecasting methods of the intensity and time development of geomagnetic and ionospheric storms

    NASA Astrophysics Data System (ADS)

    Akasofu, S.-I.

    The main phase of a geomagnetic storm develops differently from one storm to another. A description is given of the solar wind quantity which controls directly the development of the main phase of geomagnetic storms. The parameters involved include the solar wind speed, the magnetic field intensity, and the polar angle of the solar wind magnetic field projected onto the dawn-dusk plane. A redefinition of geomagnetic storm and auroral activity is given. It is pointed out that geomagnetic disturbances are caused by the magnetic fields of electric currents which are generated by the solar wind-magnetosphere dynamo. Attention is given to approaches for forecasting the occurrence and intensity of geomagnetic storms and ionospheric disturbances.

  4. The influence of geomagnetic activity on mesospheric summer echoes in middle and polar latitudes

    NASA Astrophysics Data System (ADS)

    Zeller, O.; Bremer, J.

    2009-02-01

    The dependence of mesospheric VHF radar echoes during summer months on geomagnetic activity has been investigated with observation data of the OSWIN radar in Kühlungsborn (54° N) and of the ALWIN radar in Andenes (69° N). Using daily mean values of VHF radar echoes and of geomagnetic activity indices in superimposed epoch analyses, the comparison of both data sets shows in general stronger radar echoes on the day of the maximum geomagnetic activity, the maximum value one day after the geomagnetic disturbance, and enhanced radar echoes also on the following 2-3 days. This phenomenon is observed at middle and polar latitudes and can be explained by precipitating particle fluxes during the ionospheric post storm effect. At polar latitudes, the radar echoes decrease however during and one day after very strong geomagnetic disturbances. The possible reason of this surprising effect is discussed.

  5. Range indices of geomagnetic activity

    USGS Publications Warehouse

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

    1988-01-01

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

  6. Multifractal analysis of low-latitude geomagnetic fluctuations

    NASA Astrophysics Data System (ADS)

    Bolzan, M. J. A.; Rosa, R. R.; Sahai, Y.

    2009-02-01

    The technique of large deviation multifractal spectrum has shown that the high-latitude (77.5° N, 69.2° W) geomagnetic fluctuations can be described from direct dissipation process or loading-unloading regimes of the solar wind-magnetosphere coupling. In this paper, we analyze the H-component of low-latitude (22.4° S, 43.6° W) geomagnetic field variability observed during the month of July 2000 at the Geomagnetic Observatory, Vassouras, RJ, Brazil. The variability pattern during this period is a mixture of quiet and disturbed days including the Bastille Day intense geomagnetic storm on 15 July. Due to the complexity of this data, we pursue a detailed analysis of the geomagnetic fluctuations in different time scales including a multifractal approach using the singular power spectrum deviations obtained from the wavelet transform modulus maxima (WTMM). The results suggest, as observed from high-latitude data, the occurrence of low-latitude multifractal processes driving the intermittent coupling between the solar wind-magnetosphere and geomagnetic field variations. On finer scales possible physical mechanisms in the context of nonlinear magnetosphere response are discussed.

  7. Introduction to Geomagnetic Fields

    NASA Astrophysics Data System (ADS)

    Hinze, William J.

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

  8. Historically Large Geomagnetic Storms and Potential Electric Power Grid Impacts

    NASA Astrophysics Data System (ADS)

    Kappenman, J. G.

    2004-05-01

    While recent work has been done to examine the possible Dst Intensity of historically large geomagnetic storms, the impacts caused to modern day electric power grids from these storms occurs due to rapid rate-of-change of regional geomagnetic fields which in most cases are driven by large ionospheric electrojet current intensifications. These temporally and spatially dynamic disturbance morphologies are not well-characterized by Dst or other broad geomagnetic storm indices. For estimates of storm intensity that correctly scale the threat potential to electric power grids, it is necessary to describe the rate-of-change of geomagnetic field. The rate-of-change of the geomagnetic field (dB/dt usually measured in nT/min) creates at ground level a geoelectric field that causes the flow of geomagnetically-induced currents (GIC) through ground connection points in electric power grids. Therefore in general, the larger the dB/dt, the larger the resulting geo-electric field and GIC in exposed power grid infrastructures and the greater the operational impact these induced currents will have on the power grid. Both extensive modeling analysis and recent operational experience suggests that power grids are becoming more vulnerable to geomagnetic storms as they grow in size and complexity. Also, large power grid blackouts have occurred at relatively low geomagnetic storm intensities. For example, the regional disturbance intensity that triggered the Hydro Quebec collapse during the March 13, 1989 Superstorm only reached an intensity of 479 nT/min. Large numbers of power system impacts in the United States were also observed for intensities that ranged from 300 to 600 nT/min during this storm. Yet both recent and historical data indicate that storms with disturbance levels that range from 2000 nT/min to as much ~5000 nT/min may be possible over extensive regions at latitudes of concern for large continental power grids across North America and Europe. Large GIC have also been

  9. On the slow time geomagnetic field modulation of galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Okpala, Kingsley

    2016-07-01

    Cosmic rays of galactic origin are modulated by both heliospheric and geomagnetic conditions. The mutual (and mutually exclusive) contribution of both heliospheric and geomagnetic conditions to galactic cosmic rays (GCR) modulation is still an open question. While the rapid-time association of the galactic cosmic ray variation with different heliophysical and geophysical phenomena has been well studied, not so much attention has been paid to slow-time variations especially with regards to local effects. In this work, we employed monthly means of cosmic ray count rates from two mid latitude (Hermanus and Rome), and two higher latitude (Inuvik and Oulu) neutron monitors (NM), and compared their variability with geomagnetic stations that are in close proximity to the NMs. The data spans 1966 to 2008 and covers four (4) solar cycles. The difference (DeltaCR)between the mean count rate of all days and the mean of the five quietest days for each month was compared with the Dst-related disturbance (DeltaH) derived from the nearby geomagnetic stations. Zeroth- and First- correlation between the cosmic ray parameters and geomagnetic parameters was performed to ascertain statistical association and test for spurious association. Our results show that solar activity is generally strongly correlated (>0.75) with mean strength of GCR count rate and geomagnetic field during individual solar cycles. The correlation between mean strength of cosmic ray intensity and Geomagnetic field strength is spurious and is basically moderated by the solar activity. The signature of convection driven disturbances at high latitude geomagnetic stations was evident during the declining phase of the solar cycles close to the solar minimum. The absence of this feature in the slow-time varying cosmic ray count rates in all stations, and especially in the mid latitude geomagnetic stations suggest that the local geomagnetic disturbance contributes much less in modulating the cosmic ray flux.

  10. Solar Flares and Variation of Local Geomagnetic Field: Measurements by the Huancayo Observatory over 2001-2010

    NASA Astrophysics Data System (ADS)

    Carlos Reyes, Rafael E.; Gárate Ayesta, Gabriel A.; Reyes Navarro, Felipe A.

    2017-02-01

    We study the local variation of the geomagnetic field measured by the Huancayo Geomagnetic Observatory, Peru, during 2001-2010. Initially, we sought to relate the SFI values, stored daily in the NOAA's National Geophysical Data Center, with the corresponding geomagnetic index; however, no relation was observed. Nonetheless, subsequently, a comparison between the monthly geomagnetic-activity index and the monthly SFI average allowed observing a temporal correlation between these average indices. This correlation shows that the effect of the solar flares does not simultaneously appear on the corresponding magnetic indices. To investigate this, we selected the most intense X-class flares; then, we checked the magnetic field disturbances observed in the Huancayo Geomagnetic Observatory magnetograms. We found some disturbances of the local geomagnetic field in the second and third day after the corresponding solar flare; however, the disturbance strength of the local geomagnetic field is not correlated with the X-class of the solar flare. Finally, there are some disturbances of the local geomagnetic field that are simultaneous with the X-class solar flares and they show a correlation with the total flux of the solar flare.

  11. Foundations of Geomagnetism

    NASA Astrophysics Data System (ADS)

    Jackson, Andy

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

  12. On regional geomagnetic charts

    USGS Publications Warehouse

    Alldredge, L.R.

    1987-01-01

    When regional geomagnetic charts for areas roughly the size of the US were compiled by hand, some large local anomalies were displayed in the isomagnetic lines. Since the late 1960s, when the compilation of charts using computers and mathematical models was started, most of the details available in the hand drawn regional charts have been lost. One exception to this is the Canadian magnetic declination chart for 1980. This chart was constructed using a 180 degrees spherical harmonic model. -from Author

  13. Statistical analysis of extreme values for geomagnetic and geoelectric field variations for Canada

    NASA Astrophysics Data System (ADS)

    Nikitina, Lidia; Trichtchenko, Larisa; Boteler, David

    2016-04-01

    Disturbances of the geomagnetic field produced by space weather events cause variable geoelectric fields at Earth's surface which drive electric currents in power systems, resulting in hazardous impacts on electric power transmission. In extreme cases, as during the magnetic storm in March 13, 1989, this can result in burnt-out transformers and power blackouts. To make assessment of geomagnetic and geoelectric activity in Canada during extreme space weather events, extreme value statistical analysis has been applied to more than 40 years of magnetic data from the Canadian geomagnetic observatories network. This network has archived digital data recordings for observatories located in sub-auroral, auroral, and polar zones. Extreme value analysis was applied to hourly ranges of geomagnetic variations as an index of geomagnetic activity and to hourly maximum of rate-of-change of geomagnetic field. To estimate extreme geoelectric fields, the minute geomagnetic data were used together with Earth conductivity models for different Canadian locations to calculate geoelectric fields. The extreme value statistical analysis was applied to hourly maximum values of the horizontal geoelectric field. This assessment provided extreme values of geomagnetic and geoelectric activity which are expected to happen once per 50 years and once per 100 years. The results of this analysis are designed to be used to assess the geomagnetic hazard to power systems and help the power industry mitigate risks from extreme space weather events.

  14. The national geomagnetic initiative

    NASA Technical Reports Server (NTRS)

    1993-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Soffel, H. C.

    2015-07-01

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

  16. Secular trends in storm-level geomagnetic activity

    USGS Publications Warehouse

    Love, J.J.

    2011-01-01

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

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

    USGS Publications Warehouse

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

  19. Proceedings of the Air Force Geophysics Laboratory Workshop on Geomagnetism: April 6-7, 1979.

    DTIC Science & Technology

    1979-08-20

    Proceedings of the Woikshop presented here include- 41 reports on tutorial sessions concerning magneto- spheric physics and geomagnetic pulsations, Pi4...Force Geophysics Laboratory on April 6-7, 1979 to (1) survey the present state of knowledge of the geomagnetic field during quiet and disturbed...express our appreciation to the speakers for the quality of their presentations and to the reporters who did an excellent job in summarizing the results

  20. Operational Geomagnetic Forecast Service

    NASA Astrophysics Data System (ADS)

    Semeniv, O.; Polonska, A.; Parnowski, A.

    2014-12-01

    The operational forecasting service for real-time geomagnetic indices Dst and Kp was described. The warning time for the Earth to the intersection of the Dst index is 1-4 hours, for the Kp index - 3 hours. The skillscore parameter, which is defined as a decrease of the relative mean square error with respect to the trivial model, was approximately 40% for Dst and 15% for Kp. The service works on-line freely available through STAFF http://www.staff.oma.be/ browser.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  2. Effect of March 9, 2016 Total Solar Eclipse on geomagnetic field variation

    NASA Astrophysics Data System (ADS)

    Ruhimat, Mamat; Winarko, Anton; Nuraeni, Fitri; Bangkit, Harry; Aris, M. Andi; Suwardi; Sulimin

    2016-11-01

    During solar eclipse, solar radiation to the Earth is blocked by the Moon. Thus, the ionization process in the ionosphere is disrupted, as well as the variation of geomagnetic field. The disturbance of geomagnetic field is caused by electric current in the E layer of the ionosphere. At low latitude, the current which is dominant in quiet day is the Sq currents. The blocking of solar radiation cause decrement in electron density in the blocked region. The aim of the research is to find the effect of total solar eclipse to the geomagnetic field. The measurement of the geomagnetic field variation during total solar eclipse on March 9, 2016 was carried out at the Meteorological station of BMKG in Ternate (0° 49' 45.20 "N; 127° 22' 54.00" E). By eliminating the geomagnetic disturbance that occurred in a daily geomagnetic field variation, the pattern of quiet day which is usually in a shape of smooth curve became affected. During the total solar eclipse on March 9, 2016 from 00:30 until 02:00 UT, we found that the geomagnetic field variation of the quiet day decreased by -5 nT.

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

    PubMed

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Mendoza, Blanca; Sánchez de La Peña, Salvador

    2010-08-01

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

  5. Bayesian inference in geomagnetism

    NASA Technical Reports Server (NTRS)

    Backus, George E.

    1988-01-01

    The inverse problem in empirical geomagnetic modeling is investigated, with critical examination of recently published studies. Particular attention is given to the use of Bayesian inference (BI) to select the damping parameter lambda in the uniqueness portion of the inverse problem. The mathematical bases of BI and stochastic inversion are explored, with consideration of bound-softening problems and resolution in linear Gaussian BI. The problem of estimating the radial magnetic field B(r) at the earth core-mantle boundary from surface and satellite measurements is then analyzed in detail, with specific attention to the selection of lambda in the studies of Gubbins (1983) and Gubbins and Bloxham (1985). It is argued that the selection method is inappropriate and leads to lambda values much larger than those that would result if a reasonable bound on the heat flow at the CMB were assumed.

  6. Interplanetary magnetic field-geomagnetic field coupling and vertical variance index

    NASA Astrophysics Data System (ADS)

    Abraham, A.; Renuka, G.; Cherian, L.

    2010-01-01

    The solar wind impacting at the geomagnetopause contains transient variations in the embedded interplanetary magnetic field (IMF). These disturbances are mirrored in the horizontal geomagnetic field measured at the Huancayo and Ascension Island stations. This investigation attempts to relate the microtemporal fluctuations in the IMF with the horizontal component of the geomagnetic field by means of a newly developed daily vertical variance index, which permits the quantification of such pulsations. A linear relationship is established between the disturbances observed in the interplanetary and terrestrial fields on a daily basis.

  7. Correlation Based Geomagnetic Field Modeling

    NASA Astrophysics Data System (ADS)

    Holschneider, M.; Mauerberger, S.; Lesur, V.; Baerenzung, J.

    2015-12-01

    We present a new method for determining geomagnetic field models. It is based on the construction of an a priori correlation structure derived from our knowledge about characteristic length scales and sources of the geomagnetic field. The magnetic field measurements are then seen as correlated random variables too and the inversion process amounts to compute the a posteriori correlation structure using Bayes theorem. We show how this technique allows the statistical separation of the various field contributions and the assessment of their uncertainties.

  8. Possible helio-geomagnetic activity influence on cardiological cases

    NASA Astrophysics Data System (ADS)

    Katsavrias, Christos

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

  9. New insights on geomagnetic storms from observations and modeling

    SciTech Connect

    Jordanova, Vania K

    2009-01-01

    Understanding the response at Earth of the Sun's varying energy output and forecasting geomagnetic activity is of central interest to space science, since intense geomagnetic storms may cause severe damages on technological systems and affect communications. Episodes of southward (Bzdisturbed geomagnetic 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.

  10. Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone

    NASA Astrophysics Data System (ADS)

    Edvardsen, Inge; Johnsen, Magnar G.; Løvhaug, Unni P.

    2016-10-01

    The geomagnetic field often experiences large fluctuations, especially at high latitudes in the auroral zones. We have found, using simulations, that there are significant differences in the substorm signature, in certain coordinate systems, as a function of longitude. This is confirmed by the analysis of real, measured data from comparable locations. Large geomagnetic fluctuations pose challenges for companies involved in resource exploitation since the Earth's magnetic field is used as the reference when navigating drilling equipment. It is widely known that geomagnetic activity increases with increasing latitude and that the largest fluctuations are caused by substorms. In the auroral zones, substorms are common phenomena, occurring almost every night. In principle, the magnitude of geomagnetic disturbances from two identical substorms along concurrent geomagnetic latitudes around the globe, at different local times, will be the same. However, the signature of a substorm will change as a function of geomagnetic longitude due to varying declination, dipole declination, and horizontal magnetic field along constant geomagnetic latitudes. To investigate and quantify this, we applied a simple substorm current wedge model in combination with a dipole representation of the Earth's magnetic field to simulate magnetic substorms of different morphologies and local times. The results of these simulations were compared to statistical data from observatories and are discussed in the context of resource exploitation in the Arctic. We also attempt to determine and quantify areas in the auroral zone where there is a potential for increased space weather challenges compared to other areas.

  11. 77 FR 64935 - Reliability Standards for Geomagnetic Disturbances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-24

    ... units at large generating facilities * * * a high level review will be conducted to identify and... a high level screening approach that will include transformer design, condition, geology and... require owners and operators to develop and implement a plan so that instability, uncontrolled...

  12. 78 FR 30747 - Reliability Standards for Geomagnetic Disturbances

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-23

    ... under FPA section 215(d)(5); (2) the content of the First Stage GMD Reliability Standards and the... vulnerability assessments; and (4) the content of the Second Stage GMD Reliability Standards and the schedule... expertise with respect to the content of the proposed Reliability Standards. The NOPR explicitly does...

  13. The role of SANSA's geomagnetic observation network in space weather monitoring: A review

    NASA Astrophysics Data System (ADS)

    Kotzé, P. B.; Cilliers, P. J.; Sutcliffe, P. R.

    2015-10-01

    Geomagnetic observations play a crucial role in the monitoring of space weather events. In a modern society relying on the efficient functioning of its technology network such observations are important in order to determine the potential hazard for activities and infrastructure. Until recently, it was the perception that geomagnetic storms had no or very little adverse effect on radio communication and electric power infrastructure at middle- and low-latitude regions like southern Africa. The 2003 Halloween storm changed this perception. In this paper we discuss the role of the geomagnetic observation network operated by the South African National Space Agency (SANSA) in space weather monitoring. The primary objective is to describe the geomagnetic data sets available to characterize and monitor the various types of solar-driven disturbances, with the aim to better understand the physics of these processes in the near-Earth space environment and to provide relevant space weather monitoring and prediction.

  14. Positive and negative ionospheric responses to the March 2015 geomagnetic storm from BDS observations

    NASA Astrophysics Data System (ADS)

    Jin, Shuanggen; Jin, Rui; Kutoglu, H.

    2017-01-01

    The most intense geomagnetic storm in solar cycle 24 occurred on March 17, 2015, and the detailed ionospheric storm morphologies are difficultly obtained from traditional observations. In this paper, the Geostationary Earth Orbit (GEO) observations of BeiDou Navigation Satellite System (BDS) are for the first time used to investigate the ionospheric responses to the geomagnetic storm. Using BDS GEO and GIMs TEC series, negative and positive responses to the March 2015 storm are found at local and global scales. During the main phase, positive ionospheric storm is the main response to the geomagnetic storm, while in the recovery phase, negative phases are pronounced at all latitudes. Maximum amplitudes of negative and positive phases appear in the afternoon and post-dusk sectors during both main and recovery phases. Furthermore, dual-peak positive phases in main phase and repeated negative phase during the recovery are found from BDS GEO observations. The geomagnetic latitudes corresponding to the maximum disturbances during the main and recovery phases show large differences, but they are quasi-symmetrical between southern and northern hemispheres. No clear zonal propagation of traveling ionospheric disturbances is detected in the GNSS TEC disturbances at high and low latitudes. The thermospheric composition variations could be the dominant source of the observed ionospheric storm effect from GUVI [O]/[N2] ratio data as well as storm-time electric fields. Our study demonstrates that the BDS (especially the GEO) observations are an important data source to observe ionospheric responses to the geomagnetic storm.

  15. Effect of geomagnetic activity on equatorial radio VHF scintillations and spread F

    SciTech Connect

    Rastogi, R.G.; Mullen, J.P.; MacKenzie, E.

    1981-05-01

    The paper discusses the occurrence of scintillations of ATS 3 (137 MHz) beacons recorded at Huancayo on geomagnetically quiet and disturbed days during the years 1969--1976 and compared the results with the corresponding occurrence of range and frequency spread F at Huancayo. During the equinoctial months and the December solstical months the geomgnetic activity reduces the equatorial scintillations during premidnight hours but increases their occurrence during the postmidnight hours. These features are very similar to the effect of geomagnetic activity on the occurrence of the range type of equatorial spread F rather than on the occurrence of frequency spread, which decreases for any hour of the night during geomagnetic active periods. During the June solsticial months, the occurrence of both scintillations and spread F is very much reduced; however, both the phenomena are more frequent on disturbed than on quiet days for any of the hours of the night. These effects are consistently the same for any of the years within the solar cycle. It is suggested that the equatorial radio scintillations at 137 MHz during the nighttime are produced primarily by the occurrence of the range type of spread F. The geomagnetic effects are due to the modifications of the equatorial electric field by the geomagnetic disturbance and thereby affect the development of F region irregularities causing scintillations.

  16. a Millennium of Geomagnetism

    NASA Astrophysics Data System (ADS)

    Stern, David P.

    2002-11-01

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

  17. Study of the mid-latitude ionospheric response to geomagnetic storms in the European region

    NASA Astrophysics Data System (ADS)

    Berényi, Kitti Alexandra; Barta, Veronika; Kis, Arpad

    2016-07-01

    Geomagnetic storms affect the ionospheric regions of the terrestrial upper atmosphere through different physical and atmospheric processes. The phenomena that can be regarded as a result of these processes, generally is named as "ionospheric storm". The processes depend on altitude, segment of the day, the geomagnetic latitude and longitude, strength of solar activity and the type of the geomagnetic storm. We examine the data of ground-based radio wave ionosphere sounding measurements of European ionospheric stations (mainly the data of Nagycenk Geophysical Observatory) in order to determine how and to what extent a geomagnetic disturbance of a certain strength affects the mid-latitude ionospheric regions in winter and in summer. For our analysis we used disturbed time periods between November 2012 and June 2015. Our results show significant changing of the ionospheric F2 layer parameters on strongly disturbed days compared to quiet ones. We show that the critical frequencies (foF2) increase compared to their quiet day value when the ionospheric storm was positive. On the other hand, the critical frequencies become lower, when the storm was negative. In our analysis we determined the magnitude of these changes on the chosen days. For a more complete analysis we compare also the evolution of the F2 layer parameters of the European ionosonde stations on a North-South geographic longitude during a full storm duration. The results present the evolution of an ionospheric storm over a geographic meridian. Furthermore, we compared the two type of geomagnetic storms, namely the CME caused geomagnetic storm - the so-called Sudden impulse (Si) storms- and the HSS (High Speed Solar Wind Streams) caused geomagnetic storms -the so-called Gradual storms (Gs)- impact on the ionospheric F2-layer (foF2 parameter). The results show a significant difference between the effect of Si and of the Gs storms on the ionospheric F2-layer.

  18. Extreme geomagnetically induced currents

    NASA Astrophysics Data System (ADS)

    Kataoka, Ryuho; Ngwira, Chigomezyo

    2016-12-01

    We propose an emergency alert framework for geomagnetically induced currents (GICs), based on the empirically extreme values and theoretical upper limits of the solar wind parameters and of d B/d t, the time derivative of magnetic field variations at ground. We expect this framework to be useful for preparing against extreme events. Our analysis is based on a review of various papers, including those presented during Extreme Space Weather Workshops held in Japan in 2011, 2012, 2013, and 2014. Large-amplitude d B/d t values are the major cause of hazards associated with three different types of GICs: (1) slow d B/d t with ring current evolution (RC-type), (2) fast d B/d t associated with auroral electrojet activity (AE-type), and (3) transient d B/d t of sudden commencements (SC-type). We set "caution," "warning," and "emergency" alert levels during the main phase of superstorms with the peak Dst index of less than -300 nT (once per 10 years), -600 nT (once per 60 years), or -900 nT (once per 100 years), respectively. The extreme d B/d t values of the AE-type GICs are 2000, 4000, and 6000 nT/min at caution, warning, and emergency levels, respectively. For the SC-type GICs, a "transient alert" is also proposed for d B/d t values of 40 nT/s at low latitudes and 110 nT/s at high latitudes, especially when the solar energetic particle flux is unusually high.

  19. A global analysis of the 1991 geomagnetic jerk

    NASA Astrophysics Data System (ADS)

    De Michelis, Paola; Cafarella, Lili; Meloni, Antonio

    2000-12-01

    A recent examination of the geomagnetic annual mean values for the European magnetic observatories has shown the existence of a sudden change in the secular acceleration in about 1991 (Cafarella & Meloni 1995; Macmillan 1996). Using first differences of the Y (east geomagnetic field component) mean values from 74 observatories, the worldwide character of the 1991 impulse has been determined (De Michelis et al. 1998). Using data from 109 observatories widely distributed all over the world, the structure of the secular variation for the X (north) and Z (vertical) magnetic field intensities around 1990 was investigated, and evidence of this most recent jerk was found. External effects were removed from the annual mean data by comparing the long-term variations of the geomagnetic field components at individual observatories with the long-term variations of two geomagnetic indices, aa and Dst, and of a solar index, the Wolf number R. A careful analysis has been carried out on the amplitude of the external disturbance, on its dependence on latitude, and on the weights of the geomagnetic indices in the evaluation of the resulting external field. The secular variation has been evaluated from the corrected annual means. Around 1990, the secular variation can be fitted at many observatories by two straight lines with a sudden and marked change in slope. In this manner the jerk occurrence time and the intensity of the step in the second time derivative (ΔX'', ΔY'' and ΔZ'') were computed. Maps of ΔX'', ΔY'' and ΔZ'' provide information on the worldwide intensity distribution of the examined event. Maps of the jerk occurrence-time distributions are also given. The mean jerk occurrence time is 1990.1+/-0.6. Finally, a spherical harmonic analysis was used to complete the quantitative description of this phenomenon in order to study the trend of the energy density spectrum as a function of the harmonic degree n.

  20. Simulations of the equatorial thermosphere anomaly: Geomagnetic activity modulation

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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

  1. ISEE 3 observations during the CDAW 8 intervals - Case studies of the distant geomagnetic tail covering a wide range of geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Slavin, J. A.; Owen, C. J.; Cowley, S. W. H.; Galvin, A. B.; Sanderson, T. R.; Scholer, M.

    1989-01-01

    Observations made by the ISEE 3 spacecraft in the distant geomagnetic tail during the eight CDAW 8 intervals are discussed, along with their relation to concurrent geomagnetic activity. This extensive multiinstrument case study of distant tail data covers a wide range of geomagnetic conditions from extended intervals of magnetic quiet with isolated substorms to prolonged periods of intense disturbance. Plasmoids are observed in the distant tail following disturbance enhancements, the time of their appearance being generally consistent with disconnection from the near-earth region at the time of the enhancement. Their structure is entirely consistent with the neutral line model. However, not all enhancements in geomagnetic activity result in the observation of plasmoids. In particular, the CDAW 8 data suggest that, during extended intervals of strong activity, a continuous neutral line may reside in the near-earth tail and some disturbance enhancements may then relate to an increase in the reconnection rate at a preexisting neutral line, rather than to new neutral line and plasmoid formation.

  2. Persistently anomalous Pacific geomagnetic fields

    NASA Astrophysics Data System (ADS)

    Johnson, Catherine L.; Constable, Catherine G.

    A new average geomagnetic field model for the past 3kyr (ALS3K) helps bridge a large temporal sampling gap between historical models and more traditional paleomagnetic studies spanning the last 5 Myr. A quasi-static feature seen historically in the central Pacific has the opposite sign in ALS3K; its structure is similar to, but of larger amplitude than, that in the time-averaged geomagnetic field for the last 5 Myr. Anomalous geomagnetic fields exist beneath the Pacific over timescales ranging from 10²-106 years. It is unlikely that bias over such long time scales arises from electromagnetic screening, but conceivable that the Lorentz force is influenced by long wavelength thermal variations and/or localized regions of increased electrical conductivity (associated with compositional anomalies and possibly partial melt). This is consistent with recent seismic observations of the lower mantle.

  3. Solar Influences on Geomagnetic and Related Phenomena

    NASA Technical Reports Server (NTRS)

    Vestine, E. H.

    1961-01-01

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

  4. Geomagnetic response to solar activity.

    NASA Technical Reports Server (NTRS)

    Mead, G. D.

    1972-01-01

    The relationship between solar activity and geomagnetic variations is discussed in the light of spacecraft data obtained during the last decade. The effects of centers of solar activity responsible for producing geomagnetic activity on earth are believed to be transmitted through the solar wind, and there is usually a delay of two or three days before the onset of magnetic activity. Attempts to make a one-to-one correspondence between specific solar events and specific magnetic storms, however, are usually unsuccessful, because of the complex and indirect processes linking the two phenomena. Normally, only statistical tendencies can be shown.

  5. Research on Historical Records of Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

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

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

  6. On Geomagnetism and Paleomagnetism

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    1998-01-01

    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

  7. Day-to-Day Variability of H Component of Geomagnetic Field in Central African Sector Provided by YACM (Yaoundé-Cameroon) Amber Magnetometer Station

    NASA Astrophysics Data System (ADS)

    Etoundi Messanga, Honoré

    2015-04-01

    The geomagnetic data obtained from Amber Network station in Cameroon has been used for this study. The variability of H component of geomagnetic field has been examined by using geomagnetic field data of X and Y components recorded at AMBER magnetometer station hosted by the Department of Physics of University of Yaoundé (3.87°N, 11.52°E). The day-to-day variability of the horizontal intensity of the geomagnetic field has been examined and shows that the scattering of H component of magnetic field variation is more on disturbed than on quiet days. The signatures H of geomagnetic Sq and Sd variations in intensities in the geomagnetic element, has been studied. This paper shows that the daytime variations in intensities of geomagnetic elements H, Sq(H) and Sd(H) respectively are generally greater at diurnal-times than at night-times. This study mainly interests to answer to two questions: 1) how can geomagnetic variations be used to study the equatorial ionosphere electrodynamics and electrojet equatorial over Africa in general and Cameroon in particular? 2) How can geomagnetic variations be used to monitor and predict Space weather events in Cameroon? This study presents and interprets the results of H component of geomagnetic field variations during magnetic storms and on quiet days.

  8. Emotional Disturbance

    MedlinePlus

    ... Resources of More Information References Back to top Definition We’ve chosen to use the term “emotional ... to top Characteristics As is evident in IDEA’s definition, emotional disturbances can affect an individual in areas ...

  9. Klimovskaya: A new geomagnetic observatory

    NASA Astrophysics Data System (ADS)

    Soloviev, A. A.; Sidorov, R. V.; Krasnoperov, R. I.; Grudnev, A. A.; Khokhlov, A. V.

    2016-05-01

    In 2011 Geophysical Center RAS (GC RAS) began to deploy the Klimovskaya geomagnetic observatory in the south of Arkhangelsk region on the territory of the Institute of Physiology of Natural Adaptations, Ural Branch, Russian Academy of Sciences (IPNA UB RAS). The construction works followed the complex of preparatory measures taken in order to confirm that the observatory can be constructed on this territory and to select the optimal configuration of observatory structures. The observatory equipping stages are described in detail, the technological and design solutions are described, and the first results of the registered data quality control are presented. It has been concluded that Klimovskaya observatory can be included in INTERMAGNET network. The observatory can be used to monitor and estimate geomagnetic activity, because it is located at high latitudes and provides data in a timely manner to the scientific community via the web-site of the Russian-Ukrainian Geomagnetic Data Center. The role of ground observatories such as Klimovskaya remains critical for long-term observations of secular variation and for complex monitoring of the geomagnetic field in combination with low-orbiting satellite data.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  12. Study of dominating parameters of high speed solar plasma streams in relation to cosmic ray and geomagnetic storms

    NASA Technical Reports Server (NTRS)

    Mishra, B. L.; Agrawal, S. P.

    1985-01-01

    The high speed solar wind streams observed near Earth are generally associated with the solar features, such as solar flares and coronal holes. Past studies of these streams from the two sources have revealed distinctly different effects on cosmic ray intensity, whereas the effect is similar for geomagnetic disturbances. Moreover, the effect of the magnitude of the high speed streams (V) and its rate of increase (dv/dt) has also been a subject of investigation to understand their relative contribution in producing geomagnetic disturbances. From the analysis of some of the fast streams presented here, it is difficult to predict, which one of the two (V, dv/dt) is more effective in producing geo-magnetic disturbances. Further, in most of the cases, no substantial decrease in cosmic ray intensity is observed.

  13. Johann von Lamont: A Pioneer in Geomagnetism

    NASA Astrophysics Data System (ADS)

    Soffel, Heinrich

    2006-06-01

    The 200th birthday of John Lamont (1805-1879, Figure 1), a pioneer in the study of geomagnetism, was marked on 13 December 2005. Lamont founded the Munich Geomagnetic Observatory in 1840 and was a member of the group of scientists including Carl Friedrich Gauss, Alexander von Humboldt, Eduard Sabine, Jonas Angstrøm, Humphret Lloyd, Adolf Kupffer, Karl Kreil, and Adolphe Quetelet who composed the Göttingen Magnetic Union. They organized an international network of geomagnetic observatories [Barraclough et al., 1992]. The present knowledge of the geomagnetic field and its secular variation is largely based on the data collected by the global network of geomagnetic observatories during the last 170 years. Lamont's talents and his dedication and enthusiasm for discovery are reflected in the depth and scope of his contributions to a broad variety of natural sciences such as astronomy, meteorology, geomagnetism, and geodesy. However, this article just touches on his merits in geomagnetism.

  14. Global structure of ionospheric TEC anomalies driven by geomagnetic storms

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    This study examines the structure and variability of the ionospheric TEC anomalies driven by geomagnetic storms. For this purpose the CODE global ionospheric TEC data from four geomagnetically disturbed periods (29 October-1 November 2003, 7-10 November 2004, 14-15 December 2006, and 5-6 August 2011) have been considered. By applying the tidal analysis to the geomagnetically forced TEC anomalies we made an attempt to identify the tidal or stationary planetary wave (SPW) signatures that may contribute to the generation of these anomalies. It has been found that three types of positive anomalies with different origin and different latitudinal appearance are observed. These are: (i) anomalies located near latitudes of ±40° and related to the enhancement and poleward moving of the equatorial ionization anomaly (EIA) crests; (ii) anomalies located near latitudes of ±60° and seen predominantly in the night-side ionosphere, and (iii) very high latitude anomalies having mainly zonally symmetric structure and related to the auroral heating and thermospheric expansion. The decomposition analysis revealed that these anomalies can be reconstructed as a result of superposition of the following components: zonal mean (ZM), diurnal migrating (DW1), zonally symmetric diurnal (D0), and stationary planetary wave 1 (SPW1).

  15. The impact of geomagnetic storms on the US electric power grid

    NASA Astrophysics Data System (ADS)

    Schrijver, C.; Mitchell, S.; Title, A. M.

    2012-12-01

    Large solar explosions are responsible for space weather that can impact technological infrastructure on and around Earth. We study the impacts of geomagnetic activity on the U.S. electric power grid for the period from 1992 through 2010. We find, with more than 3-sigma significance, that approximately 4% of the disturbances in the U.S. power grid reported to the U.S. Department of Energy are attributable to geomagnetic activity. The combination of our results with an economic assessment study by the electric power industry suggests that the average cost to the U.S. economy of non-catastrophic grid disturbances in which space weather conditions are a contributing factor exceeds $3 billion per year. The magnitude of this apparent economic impact warrants extensive follow-up studies to validate, understand, and mitigate against the weak but significant contribution of space weather in power grid disturbances.

  16. The reaction of the atmosphere to solar disturbances

    NASA Technical Reports Server (NTRS)

    Mikhnevich, V. V.

    1979-01-01

    The effect of solar flares on the thermosphere and the troposphere is investigated. It is found that during periods of geoeffect solar disturbances, there is a connection between phenomena in the upper and lower atmospheres and that variations in atmospheric parameters correlate with changes in the geomagnetic index.

  17. Geomagnetic Effect Caused by 1908 Tunguska Event

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    results of this current system shows that an unique azimuth of trajectory of the body exists, for which the variations of all three components of the geomagnetic field do not contradict to the observation data. This azimuth is equal to 306 degrees, while other estimates are in the range of 290-344 degrees. This idea of the atmospheric plume ejected along the trajectory and ionization in the upper atmosphere, caused by the following atmospheric oscillations, could explain the geomagnetic effect both in general and locally in Irkutsk observatory: the time delay and the variations of all magnetic field components. Binding of simulation results of observation data also allows us to select the unique trajectory azimuth for Tunguska body. References: [1] Ivanov K.G. The Geomagnetic phenomena, which were being observed on the Irkutsk magnetic observatory, following the explosion of the Tunguska meteorite //Meteoritika. 1961. Iss. XXI. P.46-49 (in Russian). [2] Losseva T., Merkin V., Nemtchinov I. Estimations of the Aeronomical and Electromagnetic Disturbances in the E-layer of the Ionosphere, caused by Tunguska Event // AGU Fall Meeting. 1999. SA32A-09.

  18. A new regard about Surlari National Geomagnetic Observatory

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    stations set on satellites circling on orbits around the Earth. In Romania, fundamental research in this field have developed within a special unit SNGO, which has followed ever since its foundation two main objectives: a permanent observation of planetary magnetic field within a world net of observatories, and rendering evident some local disturbances connected, through electromagnetic induction, to the geological structure of our country's territory. Since 1998, Romanian researchers have been allowed to take part in the largest international scientific cooperation programme in the field INTERMAGNET. Last year in SNGO was made modernize of infrastructure, techniques, apparatus and informatics system suitable for acquisition, procession and interpretation of data for a continuous and systematic study of Earth electromagnetic field. After geomagnetic field and telluric field analysis of external components (daily, semi-daily, continuous and non-continuous pulsations, disturbances magnetic storms, seismic-electric signals, etc), as well as of internal components correlated with geodynamic activity and events with natural risk. Correlative phenomenological interpretation of the results obtained by SNGO with the ones obtained by other geomagnetic observatories in the INTERMAGNET network, as well as to the possibility of separating causes at local, regional and planetary scale.

  19. Space Weather Monitoring for ISS Geomagnetic Storm Studies

    NASA Technical Reports Server (NTRS)

    Minow, Joseph I.; Parker, Linda Neergaard

    2013-01-01

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

  20. Teaching Geomagnetism in High School

    NASA Astrophysics Data System (ADS)

    Stern, D. P.

    2001-05-01

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

  1. Ice ages and geomagnetic reversals

    NASA Technical Reports Server (NTRS)

    Wu, Patrick

    1992-01-01

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

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

    USGS Publications Warehouse

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

    2011-01-01

    We study the seasonal variation of substorms, geomagnetic activity and their solar wind drivers in 1993-2008. The number of substorms and substorm mean duration depict an annual variation with maxima in Winter and Summer, respectively, reflecting the annual change of the local ionosphere. In contradiction, substorm mean amplitude, substorm total efficiency and global geomagnetic activity show a dominant annual variation, with equinoctial maxima alternating between Spring in solar cycle 22 and Fall in cycle 23. The largest annual variations were found in 1994 and 2003, in the declining phase of the two cycles when high-speed streams dominate the solar wind. A similar, large annual variation is found in the solar wind driver of substorms and geomagnetic activity, which implies that the annual variation of substorm strength, substorm efficiency and geomagnetic activity is not due to ionospheric conditions but to a hemispherically asymmetric distribution of solar wind which varies from one cycle to another. Our results imply that the overall semiannual variation in global geomagnetic activity has been seriously overestimated, and is largely an artifact of the dominant annual variation with maxima alternating between Spring and Fall. The results also suggest an intimate connection between the asymmetry of solar magnetic fields and some of the largest geomagnetic disturbances, offering interesting new pathways for forecasting disturbances with a longer lead time to the future. Copyright ?? 2011 by the American Geophysical Union.

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

    USGS Publications Warehouse

    Marsula, K.; Tanskanen, E.; Love, J.J.

    2011-01-01

    We study the seasonal variation of substorms, geomagnetic activity and their solar wind drivers in 1993–2008. The number of substorms and substorm mean duration depict an annual variation with maxima in Winter and Summer, respectively, reflecting the annual change of the local ionosphere. In contradiction, substorm mean amplitude, substorm total efficiency and global geomagnetic activity show a dominant annual variation, with equinoctial maxima alternating between Spring in solar cycle 22 and Fall in cycle 23. The largest annual variations were found in 1994 and 2003, in the declining phase of the two cycles when high-speed streams dominate the solar wind. A similar, large annual variation is found in the solar wind driver of substorms and geomagnetic activity, which implies that the annual variation of substorm strength, substorm efficiency and geomagnetic activity is not due to ionospheric conditions but to a hemispherically asymmetric distribution of solar wind which varies from one cycle to another. Our results imply that the overall semiannual variation in global geomagnetic activity has been seriously overestimated, and is largely an artifact of the dominant annual variation with maxima alternating between Spring and Fall. The results also suggest an intimate connection between the asymmetry of solar magnetic fields and some of the largest geomagnetic disturbances, offering interesting new pathways for forecasting disturbances with a longer lead time to the future.

  4. Effects of geomagnetic activity variations on the physiological and psychological state of functionally healthy humans: Some results of Azerbaijani studies

    NASA Astrophysics Data System (ADS)

    Babayev, Elchin S.; Allahverdiyeva, Aysel A.

    There are collaborative and cross-disciplinary space weather studies in the Azerbaijan National Academy of Sciences conducted with purposes of revealing possible effects of solar, geomagnetic and cosmic ray variability on certain technological, biological and ecological systems. This paper describes some results of the experimental studies of influence of the periodical and aperiodical changes of geomagnetic activity upon human brain, human health and psycho-emotional state. It also covers the conclusions of studies on influence of violent solar events and severe geomagnetic storms of the solar cycle 23 on the mentioned systems in middle-latitude location. It is experimentally established that weak and moderate geomagnetic storms do not cause significant changes in the brain's bioelectrical activity and exert only stimulating influence while severe disturbances of geomagnetic conditions cause negative influence, seriously disintegrate brain's functionality, activate braking processes and amplify the negative emotional background of an individual. It is concluded that geomagnetic disturbances affect mainly emotional and vegetative spheres of human beings while characteristics reflecting personality properties do not undergo significant changes.

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

    SciTech Connect

    Cade, W.B.

    1993-06-01

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

  6. Restoration project of geomagnetic survey in Latvia

    NASA Astrophysics Data System (ADS)

    Burlakovs, J.; Lembere, I.

    2003-04-01

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

  7. The Geomagnetic Field During a Reversal

    NASA Technical Reports Server (NTRS)

    Heirtzler, James R.

    2003-01-01

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

  8. New book discusses normal geomagnetic field

    SciTech Connect

    Pochtarev, V.I.

    1984-07-01

    Material on the normal geomagnetic field and its gradients over the Earth's surface at different elevations is presented. Methods are developed for plotting the normal geomagnetic field and mathematical approximations of the geomagnetic field are presented. The nature of the Earth's normal magnetic field is investigated on the basis of an analysis of geophysical, geological and geochemical data and data on the internal structure of the Earth.

  9. Auroral LSTIDs and SAR Arc Occurrences in Northern California During Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Bhatt, A.; Kendall, E. A.

    2015-12-01

    A 630nm allsky imager has been operated for two years in northern California at the Hat Creek Radio Observatory. F-region airglow data captured by the imager ranges from approximately L=1.7 -2.7. Since installation of the imager several geomagnetic storms have occurred with varying intensities. Two main manifestations of the geomagnetic storms are observed in the 630 nm airglow data: large-scale traveling ionospheric disturbances that are launched from the auroral zone and Stable Auroral Red (SAR) arcs during more intense geomagnetic storms. We will present a statistical analysis of these storm-time phenomena in northern California for the past eighteen months. This imager is part of a larger all-sky imaging network across the continental United States, termed MANGO (Midlatitude All-sky-imaging Network for Geophysical Observations). Where available, we will add data from networked imagers located at similar L-shell in other states as well.

  10. The Causes of Geomagnetic Storms During Solar Maximum

    NASA Technical Reports Server (NTRS)

    Tsurutani, B. T.; Gonzalez, W. D.

    1998-01-01

    One of the oldest mysteries in geomagnetism is the linkage between solar and geomagnetic activity. The 11-year cycles of both the numbers of sunspots and Earth geomagnetic storms were first noted by Sabine (1852).

  11. Sparkling Geomagnetic Field: Involving Schools in Geomagnetic Research

    NASA Astrophysics Data System (ADS)

    Bailey, Rachel; Leonhardt, Roman; Leichter, Barbara

    2014-05-01

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

  12. A case study of the thermospheric neutral wind response to geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Jiang, Guoying; Zhang, Shunrong; Wang, Wenbin; Yuan, Wei; Wu, Qian; Xu, Jiyao

    A minor geomagnetic storm (Kp=5) occurred on March 27-28, 2012. The response of the thermospheric neutral wind at ~ 250 km to this storm was investigated by the 630.0 nm nightglow measurements of Fabry-Perot interferometers (FPIs) over Xinglong (geographic location: 40.2N, 117.4E; geomagnetic location: 29.8N, 193.2E) and Millstone Hill (geographic location: 42.6N, 71.5W; geomagnetic location: 53.1N, 65.1W). Our results show that the minor storm on March 27-28, 2012 obviously effected on the thermospheric neutral winds over Xinglong and Millstone Hill, especially Millstone Hill had larger response because of its higher geomagnetic latitude. Another interesting result is that a small variation in geomagnetic activity (Kp=2.7) could enough introduce a clear disturbance in the nighttime thermospheric neutral wind over Millstone hill. NCAR-TIME-GCM (National Center for Atmospheric Research-Thermosphere Ionosphere Mesosphere Electrodynamics-General Circulation Model) was employed to study the evolution and mechanism of the thermospheric neutral wind response.

  13. Multiscale and cross entropy analysis of auroral and polar cap indices during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Gopinath, Sumesh; Prince, P. R.

    2016-01-01

    In order to improve general monoscale information entropy methods like permutation and sample entropy in characterizing the irregularity of complex magnetospheric system, it is necessary to extend these entropy metrics to a multiscale paradigm. We propose novel multiscale and cross entropy method for the analysis of magnetospheric proxies such as auroral and polar cap indices during geomagnetic disturbance times. Such modified entropy metrics are certainly advantageous in classifying subsystems such as individual contributions of auroral electrojets and field aligned currents to high latitude magnetic perturbations during magnetic storm and polar substorm periods. We show that the multiscale entropy/cross entropy of geomagnetic indices vary with scale factor. These variations can be attributed to changes in multiscale dynamical complexity of non-equilibrium states present in the magnetospheric system. These types of features arise due to imbalance in injection and dissipation rates of energy with variations in magnetospheric response to solar wind. We also show that the multiscale entropy values of time series decrease during geomagnetic storm times which reveals an increase in temporal correlations as the system gradually shifts to a more orderly state. Such variations in entropy values can be interpreted as the signature of dynamical phase transitions which arise at the periods of geomagnetic storms and substorms that confirms several previously found results regarding emergence of cooperative dynamics, self-organization and non-Markovian nature of magnetosphere during disturbed periods.

  14. Quality of GOCE accelerometer data and analysis with ionospheric dynamics during geomagnetically active days

    NASA Astrophysics Data System (ADS)

    Sinem Ince, Elmas; Fomichev, Victor; Floberghagen, Rune; Schlicht, Anja; Martynenko, Oleg; Pagiatakis, Spiros

    2016-07-01

    The Gravity field and steady-state Ocean Circulation Explorer (GOCE) was launched in March, 2009 and completed its mission with great success in November, 2011. GOCE data processing is challenging and not all the disturbances are removed from the gravitational field observations. The disturbances observed in GOCE Vyy gradients around magnetic poles are investigated by using external datasets. It is found that the amplitude of these disturbances increase during geomagnetically active days and can reach up to 5 times the expected noise level of the gradiometer. ACE (Advanced Composition Explorer) and Wind satellites measured electric field and interplanetary magnetic field components have shown that the disturbances observed in the polar regions agree with the increased solar activity. Moreover, equivalent ionospheric currents computed along ascending satellite tracks over North America and Greenland have shown a noticeable correlation with the cross-track and vertical currents and the pointing flux (ExB) components in the satellite cross track direction. Lastly, Canadian Ionosphere and Atmosphere Model (C-IAM) electric field and neutral wind simulations have shown a strong correlation of the enhancement in the ionospheric dynamics during geomagnetically active days and disturbances measured by the GOCE accelerometers over high latitudes. This may be a result of imperfect instrumentation and in-flight calibration of the GOCE accelerometers for an increased geomagnetic activity or a real disturbance on the accelerometers. We use above listed external datasets to understand the causes of the disturbances observed in gravity gradients and reduce/ eliminate them by using response analyses in frequency domain. Based on our test transfer functions, improvement is possible in the quality of the gradients. Moreover, this research also confirms that the accelerometer measurements can be useful to understand the ionospheric dynamics and space weather forecasting.

  15. History of the geomagnetic field

    USGS Publications Warehouse

    Doell, Richard R.

    1969-01-01

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

  16. Prediction of geomagnetic activity on time scales of one to ten years

    NASA Technical Reports Server (NTRS)

    Feynman, J.; Gu, X. Y.

    1986-01-01

    The long-term prediction of geomagnetic indices that characterize the state of the magnetosphere is discussed. While a prediction of the yearly average sunspot number is simultaneously a prediction of the yearly number of sudden-commencement storms, it is not a prediction of the number of disturbed or quiet half days. Knowledge of the sunspot cycle phase leads to a good estimate of the correlation expected between activity during one 27-day solar rotation period and the next.

  17. Improved geomagnetic referencing in the Arctic environment

    USGS Publications Warehouse

    Poedjono, B.; Beck, N.; Buchanan, A. C.; Borri, L.; Maus, S.; Finn, Carol; Worthington, Bill; White, Tim

    2016-01-01

    Geomagnetic referencing uses the Earth’s magnetic field to determine accurate wellbore positioning essential for success in today's complex drilling programs, either as an alternative or a complement to north-seeking gyroscopic referencing. However, fluctuations in the geomagnetic field, especially at high latitudes, make the application of geomagnetic referencing in those areas more challenging. Precise crustal mapping and the monitoring of real-time variations by nearby magnetic observatories is crucial to achieving the required geomagnetic referencing accuracy. The Deadhorse Magnetic Observatory (DED), located at Prudhoe Bay, Alaska, has already played a vital role in the success of several commercial ventures in the area, providing essential, accurate, real-time data to the oilfield drilling industry. Geomagnetic referencing is enhanced with real-time data from DED and other observatories, and has been successfully used for accurate wellbore positioning. The availability of real-time geomagnetic measurements leads to significant cost and time savings in wellbore surveying, improving accuracy and alleviating the need for more expensive surveying techniques. The correct implementation of geomagnetic referencing is particularly critical as we approach the increased activity associated with the upcoming maximum of the 11-year solar cycle. The DED observatory further provides an important service to scientific communities engaged in studies of ionospheric, magnetospheric and space weather phenomena.

  18. Interrelation of geomagnetic storms and earthquakes: Insight from lab experiments and field observations

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yuri; Kamogawa, Masashi; Novikov, Victor

    Investigations of possible relations between variations of geomagnetic field and seismicity, including Sq-variations and geomagnetic storms, are overviewed and discussed. There are many papers demonstrating positive correlations between geomagnetic field variations and subsequent earthquake occurrence that allows to authors to talk about triggering impact on earthquake source provided by ionospheric disturbances [e.g., 1]. Nevertheless, there is another opinion on negligible impact of geomagnetic disturbances on the earthquake source supported by statistical analysis of correlation between variations of geomagnetic field and global and regional seismicity. In general, the both points of view on this problem are based on statistical research without detailed consideration of possible physical mechanisms which may be involved into the supposed earthquake triggering, or very rough estimations of possible increase of stresses in the faults under critical (near-to-failure) state were made. It is clear that verification of hypothesis of earthquake triggering by geomagnetic storms should be based on physical mechanisms of generation of additional stresses in the earthquake source or some secondary mechanisms resulted in change of the fault properties. Recently it was shown that the fluids may play very important role in the electromagnetic earthquake triggering [2], and the secondary triggering mechanism should be considered when the fluid migrating into the fault under electromagnetic action may provide fault weakening up to the earthquake triggering threshold. At the same time, depending on fault orientation, local hydrological structure of the crust around the fault, location of fluid reservoirs, etc. it may be possible that the fluid migration from the fault may provide the fault strengthening, and in this case the impact of variation of geomagnetic field may provide an opposite effect, and earthquake will not occur. In so doing, it is useless to apply only

  19. Variations of terrestrial geomagnetic activity correlated to M6+ global seismic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2013-04-01

    on solar activity: protons and electrons increase in the solar wind; increase of the electromagnetic emissions on Earth's magnetic poles; reducing of the magnetopause standoff distance; intense and sudden changes in the interplanetary magnetic field (IMF). The beginning of the geomagnetic disturbance that precedes the earthquake is activated by an protons and electrons density increase in the solar wind that can be monitored through telemetric data sent by satellite ACE (Advanced Composition Explorer) that currently operating in a Lissajous orbit near the Lagrange point "L1" (between the Sun and Earth, at a distance of approximately 1.5 million km from Earth).

  20. Short-term delays (hours) of ionospheric spread F occurrence at a range of latitudes, following geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Bowman, G. G.

    1998-06-01

    The analyses have investigated the short-term responses of spread F occurrence (as identified on ionograms) at low- and middle-latitude stations to geomagnetic activity changes so that comparisons can be made with results from equatorial stations reported earlier [Bowman, 1995]. Using superposed-epoch methods, it is found that the AE index is either enhanced or depressed a few hours prior to spread F occurrence depending on whether or not low or high (respectively) spread F controls are used. The geomagnetic activity related to this inverse relationship is centered mainly around the local times of 1200 and 1800. A direct relationship is also found for geomagnetic activity which occurs in the night hours. The results for these other latitude stations are the same as those reported in the earlier paper for equatorial stations. This paper also considers for the equatorial station Huancayo extreme responses of spread F occurrence to geomagnetic activity, involving occasions of high spread F occurrence when there is a sudden drop in the level to zero for isolated days when a few hours earlier at the favored times mentioned above enhanced geomagnetic activity occurs. It is suggested that the inverse relationship involves the control of medium-scale traveling ionospheric disturbance (MS-TID) wave amplitudes by neutral-density changes, produced by large-scale traveling ionospheric disturbances (LS-TIDs) generated by geomagnetic activity concentrated mainly around the local times of 1200 and 1800. The LS-TIDs generated by geomagnetic activity at night behave differently. Height rises are produced, and as a result of the lower neutral-density levels, spread F is recorded particularly in the presunrise period. Extending the comparison of spread F characteristics at different latitudes, some comments are made on recent observations using data from satellite recordings, concerning the similarities between electron-density depletions detected for equatorial regions and those for

  1. On the watch for geomagnetic storms

    USGS Publications Warehouse

    Green, Arthur W.; Brown, William M.

    1997-01-01

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

  2. Frequency of Proterozoic geomagnetic superchrons

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  3. Minimax confidence intervals in geomagnetism

    NASA Technical Reports Server (NTRS)

    Stark, Philip B.

    1992-01-01

    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.

  4. Ionospheric response to great geomagnetic storms during solar cycle 23

    NASA Astrophysics Data System (ADS)

    Merline Matamba, Tshimangadzo; Bosco Habarulema, John

    2016-07-01

    The analyses of ionospheric responses due to great geomagnetic storms i.e. Dst index < 350 nT that occurred during solar cycle 23 are presented. The GPS Total Electron Content (TEC) and ionosonde data over Southern and Northern Hemisphere mid-latitudes were used to study the ionospheric responses. A geomagnetic latitude region of ±30° to ±46° within a longitude sector of 15° to 40° was considered. Using a criteria of Dst < -350 nT, there were only four great storm periods (29 March - 02 April 2001, 27 - 31 October 2003, 18 - 23 November 2003 and 06 - 11 November 2004) in solar cycle 23. Analysis has shown that ionospheric dynamics during these disturbed conditions could be due to a number of dynamic and electrodynamics processes in both Hemispheres. In some instances the ionosphere responds differently to the same storm condition in both Hemispheres. Physical mechanisms related to (but not limited to) composition changes and electric fields will be discussed.

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

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.

    1975-01-01

    Following some historical notes, the formation of the magnetosphere and the magnetospheric tail is discussed. The importance of electric fields is stressed and the magnetospheric convection of plasma and magnetic field lines under the influence of large-scale magnetospheric electric fields is outlined. Ionospheric electric fields and currents are intimately related to electric fields and currents in the magnetosphere and the strong coupling between the two regions is discussed. The energy input of the solar wind to the magnetosphere and upper atmosphere is discussed in terms of the reconnection model where interplanetary magnetic field lines merge or connect with the terrestrial field on the sunward side of the magnetosphere. The merged field lines are then stretched behind earth to form the magnetotail so that kinetic energy from the solar wind is converted into magnetic energy in the field lines in the tail. Localized collapses of the crosstail current, which is driven by the large-scale dawn/dusk electric field in the magnetosphere, divert part of this current along geomagnetic field lines to the ionosphere, causing substorms with auroral activity and magnetic disturbances. The collapses also inject plasma into the radiation belts and build up a ring current. Frequent collapses in rapid succession constitute the geomagnetic storm.

  6. Comparison of Dst Forecast Models for Intense Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  7. Deciphering records of geomagnetic reversals

    NASA Astrophysics Data System (ADS)

    Valet, Jean-Pierre; Fournier, Alexandre

    2016-06-01

    Polarity reversals of the geomagnetic field are a major feature of the Earth's dynamo. Questions remain regarding the dynamical processes that give rise to reversals and the properties of the geomagnetic field during a polarity transition. A large number of paleomagnetic reversal records have been acquired during the past 50 years in order to better constrain the structure and geometry of the transitional field. In addition, over the past two decades, numerical dynamo simulations have also provided insights into the reversal mechanism. Yet despite the large paleomagnetic database, controversial interpretations of records of the transitional field persist; they result from two characteristics inherent to all reversals, both of which are detrimental to an ambiguous analysis. On the one hand, the reversal process is rapid and requires adequate temporal resolution. On the other hand, weak field intensities during a reversal can affect the fidelity of magnetic recording in sedimentary records. This paper is aimed at reviewing critically the main reversal features derived from paleomagnetic records and at analyzing some of these features in light of numerical simulations. We discuss in detail the fidelity of the signal extracted from paleomagnetic records and pay special attention to their resolution with respect to the timing and mechanisms involved in the magnetization process. Records from marine sediments dominate the database. They give rise to transitional field models that often lead to overinterpret the data. Consequently, we attempt to separate robust results (and their subsequent interpretations) from those that do not stand on a strong observational footing. Finally, we discuss new avenues that should favor progress to better characterize and understand transitional field behavior.

  8. Estimating ionospheric currents by inversion from ground-based geomagnetic data and calculating geoelectric fields for studies of geomagnetically induced currents

    NASA Astrophysics Data System (ADS)

    de Villiers, J. S.; Pirjola, R. J.; Cilliers, P. J.

    2016-09-01

    This research focuses on the inversion of geomagnetic variation field measurements to obtain the source currents in the ionosphere and magnetosphere, and to determine the geoelectric fields at the Earth's surface. During geomagnetic storms, the geoelectric fields create geomagnetically induced currents (GIC) in power networks. These GIC may disturb the operation of power systems, cause damage to power transformers, and even result in power blackouts. In this model, line currents running east-west along given latitudes are postulated to exist at a certain height above the Earth's surface. This physical arrangement results in the fields on the ground being composed of a zero magnetic east component and a nonzero electric east component. The line current parameters are estimated by inverting Fourier integrals (over wavenumber) of elementary geomagnetic fields using the Levenberg-Marquardt technique. The output parameters of the model are the ionospheric current strength and the geoelectric east component at the Earth's surface. A conductivity profile of the Earth is adapted from a shallow layered-Earth model for one observatory, together with a deep-layer model derived from satellite observations. This profile is used to obtain the ground surface impedance and therefore the reflection coefficient in the integrals. The inputs for the model are a spectrum of the geomagnetic data for 31 May 2013. The output parameters of the model are spectrums of the ionospheric current strength and of the surface geoelectric field. The inverse Fourier transforms of these spectra provide the time variations on the same day. The geoelectric field data can be used as a proxy for GIC in the prediction of GIC for power utilities. The current strength data can assist in the interpretation of upstream solar wind behaviour.

  9. The geomagnetic main field and the geodynamo

    NASA Technical Reports Server (NTRS)

    Bloxham, Jeremy; Roberts, Paul H.

    1991-01-01

    Information available on the geomagnetic main field and the geodynamo is presented. Attention is given to the process of mapping the magnetic field, the last version of International Geomagnetic Reference Field Model, and maps of the magnetic field at the core-mantle boundary and their interpretation. Particular consideration is given to the existing geodynamo theories, with special relation given to the Braginsky and Meytlis theory of core turbulence in which the turbulence differs fundamentally from classical turbulence of Kolmogorov type.

  10. The International Geomagnetic Reference Field, 2005

    USGS Publications Warehouse

    Rukstales, Kenneth S.; Love, Jeffrey J.

    2007-01-01

    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/

  11. How the geomagnetic field vector reverses polarity

    USGS Publications Warehouse

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

    1985-01-01

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

  12. Geomagnetic main field modeling using magnetohydrodynamic constraints

    NASA Technical Reports Server (NTRS)

    Estes, R. H.

    1985-01-01

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

  13. Solar daily variation at geomagnetic observatories in Pakistan

    NASA Astrophysics Data System (ADS)

    Rahim, Zain; Kumbher, Abdul Salam

    2016-03-01

    A study of solar daily variation is performed using the famous Chapman-Miller method for solar cycles 22 & 23 (1986-2007). The objective is to study the characteristics of Sq variation at Pakistani geomagnetic observatories using solar harmonics and a more traditional five quietest day's method. The data recorded at the Karachi geomagnetic observatory for SC 22 and 23 and data sets from other Pakistani geomagnetic observatories; Sonmiani, Quetta and Islamabad are analyzed for H, D and Z components of the geomagnetic field. Except for the D and Z components at Karachi and Sonmiani and H component at Islamabad, the two solar daily variations correlated well with each other. Also, the synthesized daily variation from the solar harmonics of H, D and Z components explained the equivalent Sq current system reasonably well for all seasons. For H component, the first solar harmonic (s1) obtained from spherical harmonic analysis of the data, appeared as the largest harmonic with no significant changes for the seasonal division of data. However, for D and Z components, amplitudes are comparable, but undergo distinct variations. s1 for H and D components increases with magnetic activity while for Z component it is the largest for the medium phase of magnetic activity. With the sunspot number division of data, the weighted mean of the Wolf ratio of all three components is in good agreement with the previous studies. The synthesized solar daily variation for D component, S(D), at Karachi, Sonmiani, Quetta and Islamabad did not show any signs of winter anomaly for the period studied. However, S(D) variation at Karachi during winter season showed morning minimum followed by a maximum at local noon and another minimum in the afternoon. We suggest this could be the effects of Equatorial Ionospheric Anomaly (EIA) observable at the Karachi observatory only during the winter season. Similarly, much disturbed in equinoctial and summer months, S(Z) illustrated an unwavering daily

  14. Nighttime thermospheric-ionospheric coupling during geomagnetic storms

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

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

  16. The study of the midlatitude ionospheric response to geomagnetic activity at Nagycenk Geophysical Observatory

    NASA Astrophysics Data System (ADS)

    Berényi, Kitti; Kis, Árpád; Barta, Veronika; Novák, Attila

    2016-04-01

    Geomagnetic storms affect the ionospheric regions of the terrestrial upper atmosphere, causing several physical and chemical atmospheric processes. The changes and phenomena, which can be seen as a result of these processes, generally called ionospheric storm. These processes depend on altitude, term of the day, and the strength of solar activity, the geomagnetic latitude and longitude. The differences between ionospheric regions mostly come from the variations of altitude dependent neutral and ionized atmospheric components, and from the physical parameters of solar radiation. We examined the data of the ground-based radio wave ionosphere sounding instruments of the European ionospheric stations (mainly the data of Nagycenk Geophysical Observatory), called ionosonde, to determine how and what extent a given strength of a geomagnetic disturbance affect the middle latitude ionospheric regions in winter. We chose the storm for the research from November 2012 and March 2015. As the main result of our research, we can show significant differences between the each ionospheric (F1 and F2) layer parameters on quiet and strong stormy days. When we saw, that the critical frequencies (foF2) increase from their quiet day value, then the effect of the ionospheric storm was positive, otherwise, if they drop, they were negative. With our analysis, the magnitude of these changes could be determined. Furthermore we demonstrated, how a full strong geomagnetic storm affects the ionospheric foF2 parameter during different storm phases. It has been showed, how a positive or negative ionospheric storm develop during a geomagnetic storm. For a more completed analysis, we compared also the evolution of the F2 layer parameters of the European ionosonde stations on a North-South geographic longitude during a full storm duration. Therefore we determined, that the data of the ionosonde at Nagycenk Geophysical Observatory are appropriate, it detects the same state of ionosphere like the

  17. Equatorial noise emissions observed by the DEMETER spacecraft during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Němec, F.; Parrot, M.; Santolík, O.

    2016-10-01

    Equatorial noise emissions are electromagnetic waves routinely observed in the equatorial region of the inner magnetosphere at frequencies between the proton cyclotron frequency and the lower hybrid frequency. Their observations are, however, typically limited to radial distances larger than about 2RE. We use the data measured by the low-altitude DEMETER spacecraft (altitude of about 700 km) to confirm that during periods of enhanced geomagnetic activity, these emissions penetrate down to low radial distances and eventually become a dominant wave emission close to the proton cyclotron frequency in the equatorial region. Wave data obtained during six intense geomagnetic storms (Dst <- 100 nT) are analyzed. It is shown that during the analyzed time intervals, the daytime wave activity within about 20° from the geomagnetic equator is significantly enhanced, while the nightside wave activity shows a weaker increase at lower frequencies. Multicomponent wave data allow us to determine dayside wave propagation parameters. It is shown that the waves are nearly linearly polarized and their wave vector directions are almost perpendicular to the ambient Earth's magnetic field, as it has been previously observed for equatorial noise emissions. Finally, we analyze the dependence of the equatorial wave intensity at the proton cyclotron frequency on Dst and AE geomagnetic indices, and we demonstrate that the dayside wave intensity increases by as much as 3 orders of magnitude during severely disturbed periods.

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

    NASA Astrophysics Data System (ADS)

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

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

  19. Ionospheric redistribution during geomagnetic storms.

    PubMed

    Immel, T J; Mannucci, A J

    2013-12-01

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

  20. On Geomagnetism and Paleomagnetism I

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    2000-01-01

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

  1. Geomagnetically trapped anomalous cosmic rays

    SciTech Connect

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

    1995-06-01

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

  2. Substorms observations during two geomagnetically active periods in March 2012 and March 2015

    NASA Astrophysics Data System (ADS)

    Guineva, V.; Despirak, I.; Kozelov, B.

    2016-05-01

    In this work two events of strong geomagnetic activity were examined: the period 7-17 March 2012, which is one of the most disturbed periods during the ascending phase of Solar Cycle 24, and the severe geomagnetic storm on 17-20 March 2015. During the first period four consecutive magnetic storms occurred on 7, 9, 12, and 15 March. These storms were caused by Sheath, MC and HSS, and the detailed scenarios for the storms were different. The second event is a storm of fourth level with Kp = 8, the strongest one during the last four years, the so-called "St. Patrick's Day 2015 Event". A geomagnetic storm of such intensity was observed in September 2011. Our analysis was based on the 10-s sampled IMAGE magnetometers data, the 1-min sampled OMNI solar wind and interplanetary magnetic field (IMF) data and observations of the Multiscale Aurora Imaging Network (MAIN) in Apatity. The particularities in the behaviours of substorms connected with different storms during these two interesting strongly disturbed periods are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  4. Characterizing quasi-periodic disturbances in GPS TEC data and their drivers

    NASA Astrophysics Data System (ADS)

    Wurtz, J.; Coster, A. J.; Goncharenko, L.; Zhang, S.

    2012-12-01

    We examine a large data set (2003-2009) of total electron content (TEC) values derived from a global network of differential GPS receivers that was downloaded from the Madrigal database. We report on TEC oscillations at multiple periods ranging from 5 to ~30 days. A significant portion of oscillations with 9-day and 13.5-day periods is driven by the recurrent geomagnetic activity, as evident from the analysis of geomagnetic indices. The TEC disturbances in response to the recurrent geomagnetic activity are stronger at middle and high latitudes, and are less pronounced at lower latitudes (< 30 degrees). We also observe a correlation between TEC and the 28-day lunar cycle that is more evident at lower (equatorial) latitudes in both northern and southern hemispheres. The TEC disturbances associated with the lunar cycle are well pronounced during the northern hemisphere winter and equinox seasons.

  5. Bats Use Geomagnetic Field: Behavior and Mechanism

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Tian, L.; Zhang, B.; Zhu, R.

    2015-12-01

    It has been known that numerous animals can use the Earth's magnetic field for spatial orientation and long-distance navigation, nevertheless, how animals can respond to the magnetic field remain mostly ambiguous. The intensities of the global geomagnetic field varies between 23 and 66 μT, and the geomagnetic field intensity could drop to 10% during geomagnetic polarity reversals or geomagnetic excursions. Such dramatic changes of the geomagnetic field may pose a significant challenge for the evolution of magnetic compass in animals. For examples, it is vital whether the magnetic compass can still work in such very weak magnetic fields. Our previous experiment has demonstrated that a migratory bat (Nyctalus plancyi) uses a polarity compass for orientation during roosting when exposed to an artificial magnetic field (100 μT). Recently, we experimentally tested whether the N. plancyi can sense very weak magnetic fields that were even lower than those of the present-day geomagnetic field. Results showed: 1) the bats can sense the magnetic north in a field strength of present-day local geomagnetic field (51μT); 2) As the field intensity decreased to only 1/5th of the natural intensity (10 μT), the bats still responded by positioning themselves at the magnetic north. Notably, as the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT). Hence, N. plancyi is able to detect the direction of a magnetic field with intensity range from twice to 1/5th of the present-day field strength. This allows them to orient themselves across the entire range of present-day global geomagnetic field strengths and sense very weak magnetic fields. We propose that this high sensitivity might have evolved in bats as the geomagnetic field strength varied and the polarity reversed tens of times over the past fifty million years since the origin of bats. The physiological mechanisms underlying

  6. The causes of recurrent geomagnetic storms

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  7. Principles of major geomagnetic storms forecasting

    NASA Astrophysics Data System (ADS)

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

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

  8. Neutral thermosphere modelling using sectorial geomagnetic indices

    NASA Astrophysics Data System (ADS)

    Bezdek, A.; Biancale, R.; Bruinsma, S.; Lathuillere, C.; Menvielle, M.; Valette, J. J.

    Since the 1970 s semi-empirical models of neutral thermospheric density are stuck at a 10--20 precision limit with respect to observations One of the reasons for this is the use of planetary geomagnetic indices i e one value for the whole Earth at a given UT However it is well known that the atmospheric variability related to geomagnetic activity at thermospheric heights is a function while not well known of geographical location cf different physical regimes governing the polar ionosphere In our tests we made use of the so-called a lambda longitude sector geomagnetic index that depends on both the geodetic latitude and longitude the DTM-2000 model of the neutral thermospheric density and the observed densities derived from the accelerometer measurements aboard the CHAMP satellite Using the sectorial index of geomagnetic activity instead of the planetary one improves the agreement of the modelled and observed densities especially during the geomagnetic storms The DTM-2000 algorithm was modified to accommodate these indices which in fact represents the first step of its upcoming complete revision in order to benefit most from the assimilation of the CHAMP and GRACE density data

  9. Investigation of the Effects of Solar and Geomagnetic Changes on the Total Electron Content: Mid-Latitude Region

    NASA Astrophysics Data System (ADS)

    Ulukavak, Mustafa; Yalcinkaya, Mualla

    2016-04-01

    The Global Positioning System (GPS) is used as an important tool for ionosphere monitoring and obtaining the Total Electron Content (TEC). GPS satellites, positioned in the Earth's orbit, are used as sensors to investigate the space weather conditions. In this study, solar and geomagnetic activity variations were investigated between the dates 1 March-30 June 2015 for the mid-latitude region. GPS-TEC variations were calculated for each selected International GNSS Service (IGS) station in Europe. GNSS data was obtained from Crustal Dynamics Data and Information System (CDDIS) archive. Solar and geomagnetic activity indices (Kp, F10.7 ve Dst) were obtained from the Oceanic and Atmospheric Administration (NOAA), the Canadian Space Weather Forecast Centre (CSWFC) and Data Analysis Center for geomagnetism and Space Magnetism Graduate School of Science, Kyoto University (WDC) archives. GPS-TEC variations were determined for the quiet periods of the solar and geomagnetic activities. GPS-TEC changes were then compared with respect to the quiet periods of the solar and geomagnetic activities. Global Ionosphere Maps (GIM) IONEX files, obtained from the IGS analysis center, was used to check the robustness of the GPS-TEC variations. The investigations revealed that it is possible to use the GPS-TEC data for monitoring the ionospheric disturbances.

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    We use complementary observations from the prototype and expanded Global Muon Detector Network (GMDN) and the Advanced Composition Explorer (ACE) satellite to identify precursors of geomagnetic storm events. The GMDN was completed and started operation in March 2006 with the addition of the Kuwait detector, complementing the detectors at Nagoya, Hobart, and 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.

  12. Ionospheric redistribution during geomagnetic storms

    PubMed Central

    Immel, T J; Mannucci, A J

    2013-01-01

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

  13. Stratospheric Balloon Gradient Geomagnetic Measurements

    NASA Astrophysics Data System (ADS)

    Filippov, Sergey; Tsvetkov, Yury

    The study of the interior structure of the Earth and laws of its evolution is one of the most difficult problems of natural science. Among the geophysical fields the anomaly magnetic field is one of the most informational in questions of the Earth's crust structure. Many important parameters of an environment are expedient for measuring at lower altitudes, than satellite ones. So, one of the alternatives is stratospheric balloon survey. The balloon flight altitudes cover the range from 20 to 50 km. At such altitudes there are steady zone air flows due to which the balloon flight trajectories can be of any direction, including round-the-world (round-the-pole). One of the examples of such sounding system have been designed, developed and maintained at IZMIRAN during already about 20 years. This system consists of three instrumental con-tainers uniformly placed along a vertical 6 km line. System allows measuring a module and vertical gradient of the geomagnetic field along the whole flight trajectory and so one's name is -stratospheric balloon magnetic gradiometer (SMBG). The GPS-receivers, located in each instrumental container, fix the flight coordinates to within several tens meters. Data trans-mission is carried out by Globalstar satellite link. The obtained data are used in solving the problems of deep sounding of the Earth's crust magnetic structure -an extraction of magnetic anomalies, determination of a depth of bedding of magnetoactive rocks and others. The developed launching technology, deployment in flight, assembly, data processing, transfer and landing the containers with the equipment can be used for other similar problems of monitoring and sounding an environment. Useful flight weights of each instrumental container may be reaching 50 kg. More than ten testing flights (1986-2009) at stratospheric altitudes (20-30 km) have proven the reliability of this system.

  14. Geomagnetic Storm and Substorm effect on the total electron content using GPS at subauroral latitudes

    NASA Astrophysics Data System (ADS)

    Gomez, L.; Sabione, J. I.; van Zele, M. A.; Meza, A. M.; Brunini, C.

    The aim of this work is to characterize the ionospheric electron content variability during a geomagnetic storm and substorms during it This study is based on the vertical total electron content VTEC computed from global positioning system GPS GPS stations located at sub-auroral latitudes are taken into account for analyzing the signatures of the current wedge formed during the substorm expansion phase The study is focused on the geomagnetic storm befallen on April 6 and 7 2000 near the equinox Because our study is based on tying the geomagnetic disturbances with the variability of VTEC in local time the GPS stations are located at different geographic longitude The main results are a when the geomagnetic storm starts between pre-midnight and dawn a minimum of VTEC is recorded lasting all the long day ionospheric storm negative phase also the nighttime electron content may decrease below the corresponding for quiet days but near the 60z of latitude the ionization polar tongue can be observed at noon superimposed to the negative phase b the VTEC computed by GPS station placed lower than 50o recorded a positive phase when the geomagnetic storm starts between dawn and noon or a dusk effect if it starts at noon while those located between 50o and 60o show a sudden increase and later sudden decrease to nocturnal values c when it starts between afternoon and sunset the ionospheric negative phase is recorded during the next day and if the GPS station are located at higher latitude than 50o the VTEC representation shows the nocturnal end of the

  15. Magnetospheric mapping with quantitative geomagnetic field models

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  16. Quantifying Power Grid Risk from Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  17. Scaling laws from geomagnetic time series

    USGS Publications Warehouse

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

    1998-01-01

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

  18. An introduction to quiet daily geomagnetic fields

    USGS Publications Warehouse

    Campbell, W.H.

    1989-01-01

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

  19. International Geomagnetic Reference Field: the third generation.

    USGS Publications Warehouse

    Peddie, N.W.

    1982-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Gmitrov, Juraj

    2007-03-01

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

  1. GPS observation of continent-size traveling TEC pulsations at the start of geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Pradipta, R.; Valladares, C. E.; Doherty, P. H.

    2014-08-01

    We report our experimental observation of continent-size traveling plasma disturbances using GPS measurements of total electron content (TEC) over the North American sector. These plasma disturbances occurred at the beginning of geomagnetic storms, immediately after the shock arrived, and prior to the appearance of large-scale traveling ionospheric disturbances (LSTIDs) from the auroral region. Specifically, these supersize TEC perturbations were observed when the interplanetary magnetic field Bz was oscillating between northward and southward directions. They were found to propagate zonally with a propagation speed of 2-3 km/s. We interpret these TEC pulsations as ion drift waves in the magnetosphere/plasmasphere that propagate azimuthally inside the GPS orbit.

  2. On the local operational geomagnetic index K calculation

    NASA Astrophysics Data System (ADS)

    Stankov, Stan; Stegen, Koen; Wautelet, Gilles; Warnant, Rene

    2010-05-01

    There is an ongoing demand for services that can provide real-time assessment of the (global and local) geomagnetic activity and identified as being of importance to the exploration geophysics, radio communications and precise position/navigation practices, space weather research and modelling, etc. Such services depend largely on the reduction of solar, geomagnetic and ionospheric observations to generate activity indices, one of the most widely used being the K index. The K index is a quasi-logarithmic index characterising the 3-hourly range in transient magnetic activity relative to the regular "quiet-day" activity for a single site location. A derivative "planetary" index (Kp), the mean standardized K index from several globally distributed stations, provides a convenient measure of the global geomagnetic activity. Computer-based derivation of K/Kp indices was a major step towards higher efficiency and lower costs. Nowadays, automated data acquisition, processing and generating the index in real time is mandatory for any reliable service. However, Kp may not be accurate enough when monitoring disturbances of smaller scale, so the local K index (derived from the nearest magnetic station/s) might be considered as the better choice. Moreover, the 3-hour time scale is much larger than the shorter characteristic time of localised ionospheric phenomena that are of particular interest to us. Our experience in developing a novel nowcast system for local operational geomagnetic index K calculation (K-LOGIC) will be presented. The system is based on a fully automated computer procedure for real-time digital magnetogram data acquisition, screening the dataset and removing the outliers, establishing the solar regular (Sr) variation of the geomagnetic field, calculating the K index, and issuing an alert if storm-level activity is indicated. This is a time-controlled (rather than event-driven) system delivering as regular output (time resolution set to 1 hour) the K value

  3. The causes of geomagnetic storms during solar maximum

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce T.; Gonzalez, Walter D.

    1994-01-01

    One of the oldest mysteries in geomagnetism is the linkage between solar and geomagnetic activity. In investigating the causes of geomagnetic storms occurring during solar maximum, the following topics are discussed: solar phenomena; types of solar wind; magnetic reconnection and magnetic storms; an interplanetary example; and future space physics missions.

  4. Satellite Data for Geomagnetic Field Modeling

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  5. Satellite data for geomagnetic field modeling

    NASA Astrophysics Data System (ADS)

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

    1992-06-01

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

  6. Anencephalus, drinking water, geomagnetism and cosmic radiation.

    PubMed

    Archer, V E

    1979-01-01

    The mortality rates from anencephalus from 1950-1969 in Canadian cities are shown to be strongly correlated with city growth rate and with horizontal geomagnetic flux, which is directly related to the intensity of cosmic radiation. They are also shown to have some association with the magnesium content of drinking water. Prior work with these data which showed associations with magnesium in drinking water, mean income, latitude and longitude was found to be inadequate because it dismissed the observed geographic associations as having little biological meaning, and because the important variables of geomagnetism and city growth rate were overlooked.

  7. Polar and equatorial ionosphere interaction during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Biktash, L.

    The solar wind-magnetosphere-ionosphere coupling as applied to the polar and equatorial ionosphere dynamics is examined. To do this simultaneous observations of the IMF, ground-based measurements of the ionospheric parameters and geomagnetic field variations from the high latitudes to the equator are used during magnetic storms. It is shown that the auroral electric fields during magnetically disturbed conditions by the magnetospheric current systems can play a dominant role in the equatorial ionosphere processes. During magnetic storms the equatorial ionosphere parameters h'F, foF2 and etc. widely deviated from quiet day conditions and different kinds of ionospheric irregularities are formed. The equatorial ionospheric irregularities manifest as spread F in ionograms, reversals of drift velocities, scintillation of radio transmissions through the ionosphere, etc. These phenomena can interpret as the result of direct penetration of electric fields from the high latitude field-aligned currents (FAC) to the equatorial ionosphere. Model of direct penetration of FAC electric field of Polar Regions 1 and Region 2, which are controlled by the solar wind, to the equatorial ionosphere is presented. From this model the solar wind electric field through the FAC is likely to the factor wich generate or inhibit the equatorward penetration of the high latitude electric field. We demonstrate that the model is suitable to explain h'F, foF2 variations and scintillation activity during geomagnetic storms. Taking into account of the equatorial and auroral electric fields coupling, relationship, between these regions can be useful to study difficult auroral conditions during magnetic storms.

  8. Calibration of historical geomagnetic observations from Prague-Klementinum

    NASA Astrophysics Data System (ADS)

    Hejda, Pavel

    2015-04-01

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

  9. Frequency and duration of disturbances in the mid-latitude F region of the ionosphere

    SciTech Connect

    Lambert, S.

    1988-08-01

    Disturbances of the ionospheric F region at two well-separated midlatitude stations were identified on rapid run ionograms by spread echoes, blackouts, and anomalies in structure or critical frequency. The diurnal variation in the probability of disturbance consistently shows minima around sunrise and sunset. Details such as a brief postsunset enhancement in winter are revealed by the fine time resolution of the data. Disturbance probabilities were lowest in autumn and spring (8 and 9 percent), while that for winter (33 percent) exceeded the summer level (20 percent). Spread F constituted 32 percent of the events, and disturbances producing sharply defined ionogram signatures 77 percent, with some overlapping of types. The majority of disturbances were not correlated with geomagnetic phenomena. Disturbances at the two stations were essentially independent (spatial correlation of 0.15). Spread F events were of longer duration (25 min) than sharp disturbances (20 min). 24 references.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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

  11. Episodes of Ionospheric Disturbances caused by Solar Activity probed using Long Wave Terrestrial Radio Signals

    NASA Astrophysics Data System (ADS)

    Shanmugha Sundaram, GA; Shaik, Manoj

    2016-07-01

    The dynamic spectral record of long wave (LW) radio signals (kHz band) had registered a disturbed condition of the ionosphere region involved with propagation of these signals. The reason for such signatures in the dynamic spectrogram can be accredited to the impact of Solar Energetic Particles (SEP) on the ionosphere along the propagation path of terrestrial long wave radiation, studied using the Multi-Hop propagation model. Points of reflection in the ionosphere directly above specific locations above the Earth where determined. Total Electron Content (TEC) values for such regions were obtained from interpretation of the global positioning system (GPS) data. From a comparisons of such results during periods when the Sun was quiet and active, the magnitude of ionosphere disturbance contributed by the various active solar phenomenae has been determined. The work reported here is based on the impact of Geomagnetic storm (K_{p}=6) on the TEC, that occurred on 16 April 2015. LW radio signals from transmitter locations operated by the United States Navy near Lualualei, Hawaii (Geomagnetic lat 21°25'13.38"}N, Geomagnetic long 158°09'14.35"W) and by France at Rosnay (Geomagnetic lat 46°42'47"N, Geomagnetic long 1°14'39"E) were monitored closely to know the extent of ionospheric impact.

  12. On the causes of geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.

    1975-01-01

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

  13. Geomagnetic referencing in the arctic environment

    USGS Publications Warehouse

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

    2011-01-01

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

  14. Geomagnetic referencing in the arctic environment

    USGS Publications Warehouse

    Poedjono, B.; Beck, N.; Buchanan, A. C.; Brink, J.; Longo, J.; Finn, C.A.; Worthington, E.W.

    2011-01-01

    Geomagnetic referencing is becoming an increasingly attractive alternative to north-seeking gyroscopic surveys to achieve the precise wellbore positioning essential for success in today's complex drilling programs. However, the greater magnitude of variations in the geomagnetic environment at higher latitudes makes the application of geomagnetic referencing in those areas more challenging. Precise, real-time data on those variations from relatively nearby magnetic observatories can be crucial to achieving the required accuracy, but constructing and operating an observatory in these often harsh environments poses a number of significant challenges. Operational since March 2010, the Deadhorse Magnetic Observatory (DED), located in Deadhorse, Alaska, was created through collaboration between the United States Geological Survey (USGS) and a leading oilfield services supply company. DED was designed to produce real-time geomagnetic data at the required level of accuracy, and to do so reliably under the extreme temperatures and harsh weather conditions often experienced in the area. The observatory will serve a number of key scientific communities as well as the oilfield drilling industry, and has already played a vital role in the success of several commercial ventures in the area, providing essential, accurate data while offering significant cost and time savings, compared with traditional surveying techniques. Copyright 2011, Society of Petroleum Engineers.

  15. Geomagnetic storms: historical perspective to modern view

    NASA Astrophysics Data System (ADS)

    Lakhina, Gurbax S.; Tsurutani, Bruce T.

    2016-12-01

    The history of geomagnetism is more than 400 years old. Geomagnetic storms as we know them were discovered about 210 years ago. There has been keen interest in understanding Sun-Earth connection events, such as solar flares, CMEs, and concomitant magnetic storms in recent times. Magnetic storms are the most important component of space weather effects on Earth. We give an overview of the historical aspects of geomagnetic storms and the progress made during the past two centuries. Super magnetic storms can cause life-threatening power outages and satellite damage, communication failures and navigational problems. The data for such super magnetic storms that occurred in the last 50 years during the space era is sparce. Research on historical geomagnetic storms can help to create a database for intense and super magnetic storms. New knowledge of interplanetary and solar causes of magnetic storms gained from spaceage observations will be used to review the super magnetic storm of September 1-2, 1859. We discuss the occurrence probability of such super magnetic storms, and the maximum possible intensity for the effects of a perfect ICME: extreme super magnetic storm, extreme magnetospheric compression, and extreme magnetospheric electric fields.

  16. Incorporation of geomagnetic data and services into EPOS infrastructure

    NASA Astrophysics Data System (ADS)

    Hejda, Pavel; Chambodut, Aude; Curto, Juan-Jose; Flower, Simon; Kozlovskaya, Elena; Kubašta, Petr; Matzka, Jürgen; Tanskanen, Eija; Thomson, Alan

    2016-04-01

    Monitoring of the geomagnetic field has a long history across Europe that dates back to 1830', and is currently experiencing an increased interest within Earth observation and space weather monitoring. Our goals within EPOS-IP are to consolidate the community, modernise data archival and distribution formats for existing services and create new services for magnetotelluric data and geomagnetic models. Specific objectives are: • Enhance existing services providing geomagnetic data (INTERMAGNET- INTErnational Real-time MAGnetic observatory NETwork; World Data Centre for Geomagnetism; IMAGE- International Monitor for Auroral Geomagnetic Effects) and existing services providing geomagnetic indices (ISGI - International Service of Geomagnetic Indices). • Develop and enhance the geomagnetic community's metadata systems by creating a metadata database, filling it and putting in place processes to ensure that it is kept up to date in the future. • Develop and build access to magnetotelluric (MT) data including transfer functions and time series data from temporary, portable MT-arrays in Europe, as well as to lithospheric conductivity models derived from TM-data. • Develop common web and database access points to global and regional geomagnetic field and conductivity models. • Establish links from the geomagnetic data services, products and models to the Integrated Core Services. The immediate task in the current period is to identify data models of existing services, modify them and integrate into a common model of Geomagnetic Thematic Core Services.

  17. Radiometric Quantification of Aurora Activities during Severe Geomagnetic Storms from SNPP VIIRS Day-Night Band Observations

    NASA Astrophysics Data System (ADS)

    Shao, X.; Cao, C.; Liu, T. C.; Zhang, B.; Fung, S. F.; Sharma, A. S.

    2015-12-01

    Two severe geomagnetic storms of level G4 occurred so far in 2015. These are among the strongest geomagnetic storms of the current solar cycle (Solar Cycle 24). Both reached G4-Severe level (Kp = 8) on March 17, 2015 and on June 22, 2015, respectively. The March 17 geomagnetic storm is identified as due to the Coronal Mass Ejections (CMEs) which erupted on March 15 from Region 2297 of solar surface. Combined effects of three CMEs produced on June 18, 19 and 21 caused G4-Severe geomagnetic storm on June 22, 2015. During these geomagnetic storms, solar wind interacts with the Earth's magnetic field and causes temporary disturbances of the Earth's magnetosphere and aurora may be seen in low latitude region. The Day Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi-NPP represents a major advancement in night time imaging capabilities. The DNB senses radiance spanning 7 orders of magnitude in one (0.5-0.9 μm) reflective solar band and provides imagery over illumination levels ranging from full sunlight to quarter moon. In this paper, DNB observations of aurora activities during the two geomagnetic storm events are analyzed. During these events, auroras are observed to evolve with salient features by DNB during orbital pass on the night side (~local time 1:30am) in both hemispheres. The radiometricly calibrated DNB observations allow us to quantitatively analyze the large-scale spatial distribution and temporal evolution of aurora during the geomagnetic storms. The radiance data from DNB observation are collected at the night sides of both hemispheres during the two events and geo-located onto geomagnetic local time (MLT) coordinates. Regions of aurora during each orbital pass are identified through image processing by contouring radiance values and excluding regions with stray light near day-night terminator. The evolution of aurora are characterized with time series of the poleward and low latitude boundary of aurora, their

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

    USGS Publications Warehouse

    Green, A.W.

    1990-01-01

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

  19. The 27 day solar rotational effect on mesospheric nighttime OH and O3 observations induced by geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Fytterer, T.; Santee, M. L.; Sinnhuber, M.; Wang, S.

    2015-09-01

    Observations performed by the Earth Observing System Microwave Limb Sounder instrument on board the Aura satellite from 2004 to 2009 (2004 to 2014) were used to investigate the 27 day solar rotational cycle in mesospheric OH (O3) and the physical connection to geomagnetic activity. Data analysis was focused on nighttime measurements at geomagnetic latitudes connected to the outer radiation belts (55°N/S-75°N/S). The applied superposed epoch analysis reveals a distinct 27 day solar rotational signal in OH and O3 during winter in both hemispheres at altitudes >70 km. The OH response is positive and in-phase with the respective geomagnetic activity signal, lasting for 1-2 days. In contrast, the O3 feedback is negative, delayed by 1 day, and is present up to 4 days afterward. Largest OH (O3) peaks are found at ~75 km, exceeding the 95% significance level and the measurement noise of <2% (<0.5%), while reaching variations of +14% (-7%) with respect to their corresponding background. OH at 75 km is observed to respond to particle precipitation only after a certain threshold of geomagnetic activity is exceeded, depending on the respective OH background. The relation between OH and O3 at 75 km in both hemispheres is found to be nonlinear. In particular, OH has a strong impact on O3 for relatively weak geomagnetic disturbances and accompanying small absolute OH variations (<0.04 ppb). In contrast, catalytic O3 depletion is seen to slow down for stronger geomagnetic variations and OH anomalies (0.04-0.13 ppb), revealing small variations around -0.11 ppm.

  20. The 27 day solar rotational effect on mesospheric nighttime OH and O3 observations induced by geomagnetic activity.

    PubMed

    Fytterer, T; Santee, M L; Sinnhuber, M; Wang, S

    2015-09-01

    Observations performed by the Earth Observing System Microwave Limb Sounder instrument on board the Aura satellite from 2004 to 2009 (2004 to 2014) were used to investigate the 27 day solar rotational cycle in mesospheric OH (O3) and the physical connection to geomagnetic activity. Data analysis was focused on nighttime measurements at geomagnetic latitudes connected to the outer radiation belts (55°N/S-75°N/S). The applied superposed epoch analysis reveals a distinct 27 day solar rotational signal in OH and O3 during winter in both hemispheres at altitudes >70 km. The OH response is positive and in-phase with the respective geomagnetic activity signal, lasting for 1-2 days. In contrast, the O3 feedback is negative, delayed by 1 day, and is present up to 4 days afterward. Largest OH (O3) peaks are found at ~75 km, exceeding the 95% significance level and the measurement noise of <2% (<0.5%), while reaching variations of +14% (-7%) with respect to their corresponding background. OH at 75 km is observed to respond to particle precipitation only after a certain threshold of geomagnetic activity is exceeded, depending on the respective OH background. The relation between OH and O3 at 75 km in both hemispheres is found to be nonlinear. In particular, OH has a strong impact on O3 for relatively weak geomagnetic disturbances and accompanying small absolute OH variations (<0.04 ppb). In contrast, catalytic O3 depletion is seen to slow down for stronger geomagnetic variations and OH anomalies (0.04-0.13 ppb), revealing small variations around -0.11 ppm.

  1. Ionosphere data assimilation capabilities for representing the high-latitude geomagnetic storm event in September 2011

    NASA Astrophysics Data System (ADS)

    Solomentsev, Dmitry; Jacobsen, Knut Stanley; Khattatov, Boris; Khattatov, Vyacheslav; Cherniak, Yakov; Titov, Anton

    2014-12-01

    Severe geomagnetic storms have a strong impact on space communication and satellite navigation systems. Forecasting the appearance of geomagnetically induced disturbances in the ionosphere is one of the urgent goals of the space weather community. The challenge is that the processes governing the distribution of the crucial ionospheric parameters have a rather poor quantitative description, and the models, built using the empirical parameterizations, have limited capabilities for operational purposes. On the other hand, data assimilation techniques are becoming more and more popular for nowcasting the state of the large-scale geophysical systems. We present an example of an ionospheric data assimilation system performance assessment during a strong geomagnetic event, which took place on 26 September 2011. The first-principle model has assimilated slant total electron content measurements from a dense network of ground stations, provided by the Norwegian Mapping Authority. The results have shown satisfactory agreement with independent data and demonstrate that the assimilation model is accurate to about 2-4 total electron content units and can be used for operational purposes in high-latitude regions. The operational system performance assessment is the subject of future work.

  2. Impact of famous CEDAR, GEM and ISTP geomagnetic Storms on HF Radio Propagation

    NASA Astrophysics Data System (ADS)

    Blagoveshchensky, D.; Sergeeva, M.

    The mighty geomagnetic storms due to the extraordinary Sun s activity cause as a rule some impacts in these areas radiation effects on human and satellites commercial airlines outages electric power and other geomagnetic effects navigation and communication GPS effects ionospheric disturbances HF communication effects Therefore our scientific understanding of this activity is very important Joint efforts for example within the framework of the CAWSES enable progress in our ability to i identify critical inputs to specify the geospace environment at a level needed to minimize impacts on technology human society and life and ii support the development of robust models that predict conditions in geospace based on understanding of the Sun-Earth system and all of its interacting components In this study influence of 14 geomagnetic storms from a list of CEDAR GEM and ISTP storms within 1997-99 on radio propagation conditions have been investigated These conditions were estimated through variations of the MOF and LOF the maximum and lowest operation frequencies on each path from three high-latitude HF radio paths of North-west Russia before during and after a storm It was shown that the storm impact on the ionosphere and radio propagation for each storm has an individual character Nevertheless the common character of the certain manifestations during storm-time was revealed For example the frequency range MOF - LOF is getting wider several hours before a storm then it is sharply narrow during a storm-time and further it is expanded again several

  3. Equatorial electrojet in the Indian region during the geomagnetic storm of 13-14 November 1998

    NASA Astrophysics Data System (ADS)

    Chandra, H.; Rastogi, R. G.; Choudhary, R. K.; Sharma, Som

    2016-04-01

    The geomagnetic storm of November 1998 is a unique event where IMF-Bz remained southward with values exceeding -15 nT for more than a day. The SYM/H index decreased from about 07 hr on 13 November 1998 reaching a minimum of about -120 nT around midnight of 13-14 November 1998. Features of the equatorial electrojet in the Indian region are studied during the geomagnetic storm event of 13-14 November 1998, based on the geomagnetic data from the chain of observatories in India. Sudden northward turning of IMF-Bz for a very short duration around 08 hr on 13 November 1998 resulted in a small and very short duration counter electrojet. A strong (-50 nT) and a long duration counter electrojet, right from 08 to 13 hr on 14 November 1998 was observed resulting in the absence of equatorial Es at Thumba. Absence of the equatorial ionization anomaly was also observed as seen from the ionograms over Thumba and ionspheric data from Ahmedabad. The delayed effect on 14 November 1998 is due to the disturbance dynamo effect.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    1992-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  7. Geomagnetic modeling by optimal recursive filtering

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  8. Fluctuations in tides and geomagnetic variations

    NASA Astrophysics Data System (ADS)

    Kohsiek, A.; Kiefer, M.; Meek, C. E.; Manson, A. H.

    Middle atmosphere tidal winds and the daily geomagnetic Sq-variation show a day-to-day variability, both with a local behaviour. Due to the main cause of the Sq-variation, the ionospheric dynamo effect, day-to-day fluctuation of Sq could be raised by fluctuations in tides. This coupling of fluctuations is investigated with radar wind data measured at Saskatoon at around 100 km height and with magnetic data from four observatories in the vicinity of the radar. We show that our definition of fluctuations exhibits properties of atmospheric tides in the winds and that the magnetic data can be assumed to represent a local behaviour. We find that there are some significant correlations between fluctuations in winds and magnetic variations. Apparently the local fluctuation of geomagnetic variations is weakly coupled not only to the fluctuations of the semidiurnal tides but also to those of the mean winds.

  9. Solar wind charge exchange during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Robertson, I. P.; Cravens, T. E.; Sibeck, D. G.; Collier, M. R.; Kuntz, K. D.

    2012-04-01

    On 2001 March 31 a coronal mass ejection pushed the subsolar magnetopause to the vicinity of geosynchronous orbit at 6.6 R_E. The NASA/GSFC Community Coordinated Modeling Center (CCMC) 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 soft 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 2000 July 14 (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.

  10. MAGSAT for geomagnetic studies over Indian region

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  11. NOAA Plans for Geomagnetic Storm Observations

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Sharma, A. K.; et al.

    2006-11-01

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

  13. Survey of Geomagnetic Observations Made in the Northern Sector of Russia and New Methods for Analysing Them

    NASA Astrophysics Data System (ADS)

    Gvishiani, Alexei; Lukianova, Renata; Soloviev, Anatoly; Khokhlov, Andrei

    2014-09-01

    An overview of the geomagnetic observations made in the northern part of Russia is presented from a historical perspective. Several stations were deployed on the territory of the former Soviet Union during the International Geophysical Year, 1957-1958, with the active participation and guidance of the Interagency Geophysical Committee which is inherited by the Geophysical Center of the Russian Academy of Sciences (GC RAS). In the 1990s, the majority of these stations, especially those in the remoter regions, were closed. Nowadays, the geomagnetic network, including the observatories of the INTERMAGNET program, has been restored. Examples of high-latitude geomagnetic variations in the Russian longitudinal sector are shown, and maps and trends of the secular variation over the territory of Russia presented. Particular attention is paid to the automated processing of data and to the analysis methods used. To process the growing amount of high-resolution geomagnetic data, sophisticated mathematical methods based on the fuzzy logic approach and new discrete mathematical analysis algorithms have been developed. The formal methods and algorithms for recognizing both artificial and natural disturbances in the magnetograms are described.

  14. An association between geomagnetic activity and dream bizarreness.

    PubMed

    Lipnicki, Darren M

    2009-07-01

    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.

  15. Geomagnetic Jerks in the Swarm Era

    NASA Astrophysics Data System (ADS)

    Brown, William; Beggan, Ciaran; Macmillan, Susan

    2016-08-01

    The timely provision of geomagnetic observations as part of the European Space Agency (ESA) Swarm mission means up-to-date analysis and modelling of the Earth's magnetic field can be conducted rapidly in a manner not possible before. Observations from each of the three Swarm constellation satellites are available within 4 days and a database of close-to-definitive ground observatory measurements is updated every 3 months. This makes it possible to study very recent variations of the core magnetic field. Here we investigate rapid, unpredictable internal field variations known as geomagnetic jerks. Given that jerks represent (currently) unpredictable changes in the core field and have been identified to have happened in 2014 since Swarm was launched, we ask what impact this might have on the future accuracy of the International Geomagnetic Reference Field (IGRF). We assess the performance of each of the IGRF-12 secular variation model candidates in light of recent jerks, given that four of the nine candidates are novel physics-based predictive models.

  16. AI techniques in geomagnetic storm forecasting

    NASA Astrophysics Data System (ADS)

    Lundstedt, Henrik

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

  17. Geomagnetic secular variation in the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Heirtzler, J. R.; Nazarova, K.

    2003-02-01

    Annual repeat stations in Australia and in South Africa show that secular variation may change rapidly and over short geographical distances in the Indian Ocean area. Satellite models show large secular variations in the center of the Indian Ocean where there are few island geomagnetic observatories. This paper investigates marine geomagnetic measurements to see if they give more information about secular variations in this area. Between 1960 and 1988 there were more than 70 port-to-port cruises with ships towing proton precession magnetometers in the Indian Ocean. Change in field intensity from one cruise to another provides new information about the secular variation in this part of the world. Several methods were investigated to determine this change from the ship's data. Observing the change on closely parallel or crossing tracks provides an estimate of this change. These results indicate that there are short time and distance scales of secular variation in the Indian Ocean which have not been accounted for in geomagnetic field models.

  18. Domino model for geomagnetic field reversals.

    PubMed

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

    2013-01-01

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

  19. Solar generated quasi-biennial geomagnetic variation

    NASA Technical Reports Server (NTRS)

    Sugiura, M.; Poros, D. J.

    1977-01-01

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

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

    SciTech Connect

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

    1999-10-07

    The Black Thunder Coal Mine (BTCM) near Gillette, Wyoming was used as a test bed to determine the feasibility of detecting explosion-induced geomagnetic disturbances with ground-based induction magnetometers. Two magnetic observatories were fielded at distances of 50 km and 64 km geomagnetically north from the northernmost edge of BTCM. Each observatory consisted of three separate but mutually orthogonal magnetometers, Global Positioning System (GPS) timing, battery and solar power, a data acquisition and storage system, and a three-axis seismometer. Explosions with yields of 1 to 3 kT of TNT equivalent occur approximately every three weeks at BTCM. We hypothesize that explosion-induced acoustic waves propagate upward and interact collisionally with the ionosphere to produce ionospheric electron density (and concomitant current density) perturbations which act as sources for geomagnetic disturbances. These disturbances propagate through an ionospheric Alfven waveguide that we postulate to be leaky (due to the imperfectly conducting lower ionospheric boundary). Consequently, wave energy may be observed on the ground. We observed transient pulses, known as Q-bursts, with pulse widths about 0.5 s and with spectral energy dominated by the Schumann resonances. These resonances appear to be excited in the earth-ionosphere cavity by Alfven solitons that may have been generated by the explosion-induced acoustic waves reaching the ionospheric E and F regions and that subsequently propagate down through the ionosphere to the atmosphere. In addition, we observe late time (> 800 s) ultra low frequency (ULF) geomagnetic perturbations that appear to originate in the upper F region ({approximately}300 km) and appear to be caused by the explosion-induced acoustic wave interacting with that part of the ionosphere. We suggest that explosion-induced Q-bursts may be discriminated from naturally occurring Q-bursts by association of the former with the late time explosion-induced ULF

  1. Geomagnetic Field Response at Southern and Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Chandel, Babita

    Geomagnetic Field Response at Southern and Northern Hemisphere Babita Chandel, Shailendra Saini, Sneha Yadav,S.K.Vijay and A.K.Gwal Space Science Laboratory, Department of Physics, Barkatullah University, Bhopal-462026, India ABSTRACT: This paper represents the geomagnetic field response at Southern Hemisphere (MAITRI) and Northern Hemisphere (TROMSO). The Indian Antarctic Station MAITRI is located at geomagnetic Long. (66.030, 53.210) where as TROMSO is at geomagnetic Long. (66.030, 53.210). We studied the behaviour of geomagnetic field with respect to geomagnetic storms at both the stations TROMSO and MAITRI. It was observed that at Southern Hemisphere there is more variation in winter as compared to the summer season, where as in Northern Hemisphere the variations are more in summer as compared to winter. As in the Northern hemisphere the magnetospheric plasma is strongly turbulized in summer and in Southern hemisphere the magentospheric plasma is strongly turbulized in winter.

  2. The Vector Matching Method in Geomagnetic Aiding Navigation.

    PubMed

    Song, Zhongguo; Zhang, Jinsheng; Zhu, Wenqi; Xi, Xiaoli

    2016-07-20

    In this paper, a geomagnetic matching navigation method that utilizes the geomagnetic vector is developed, which can greatly improve the matching probability and positioning precision, even when the geomagnetic entropy information in the matching region is small or the geomagnetic contour line's variety is obscure. The vector iterative closest contour point (VICCP) algorithm that is proposed here has better adaptability with the positioning error characteristics of the inertial navigation system (INS), where the rigid transformation in ordinary ICCP is replaced with affine transformation. In a subsequent step, a geomagnetic vector information fusion algorithm based on Bayesian statistical analysis is introduced into VICCP to improve matching performance further. Simulations based on the actual geomagnetic reference map have been performed for the validation of the proposed algorithm.

  3. The Vector Matching Method in Geomagnetic Aiding Navigation

    PubMed Central

    Song, Zhongguo; Zhang, Jinsheng; Zhu, Wenqi; Xi, Xiaoli

    2016-01-01

    In this paper, a geomagnetic matching navigation method that utilizes the geomagnetic vector is developed, which can greatly improve the matching probability and positioning precision, even when the geomagnetic entropy information in the matching region is small or the geomagnetic contour line’s variety is obscure. The vector iterative closest contour point (VICCP) algorithm that is proposed here has better adaptability with the positioning error characteristics of the inertial navigation system (INS), where the rigid transformation in ordinary ICCP is replaced with affine transformation. In a subsequent step, a geomagnetic vector information fusion algorithm based on Bayesian statistical analysis is introduced into VICCP to improve matching performance further. Simulations based on the actual geomagnetic reference map have been performed for the validation of the proposed algorithm. PMID:27447645

  4. Ionospheric disturbances at the equatorial anomaly crest region during the March 1989 magnetic storms

    SciTech Connect

    Yinn-Nien Huang; Kang, Cheng )

    1991-08-01

    On March 6, 1989, the largest sunspot group since 1982 came into view as it moved out of the eastern limb of the Sun. It was highly active during March8-18, and a great many transient ionospheric and geomagnetic variations were triggered by this sunspot group. The intensive ionospheric observations at Lunping Observatory and Chungli Ionosphere Station during this period recorded 30 solar flares manifested as shortwave fade-outs, sudden frequency deviations, and solar flare effects and three storm sudden commencement (SSC)-tupe geomagnetic storms, among which the March 13 SSC-type geomagnetic storm triggered an unusually severe ionospheric disturbance. The ionospheric total electron content, the critical frequency of the F{sub 2} layer, f{sub o}F{sub 2}, and the virtual heights at given frequencies all show wavelike up-and-down oscillations of the ionosphere. This oscillatory ionospheric motion is explained as due to the compression and expansion of the plasmasphere.

  5. Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

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

  6. Has the Next Geomagnetic Field Reversal Already Started?

    NASA Astrophysics Data System (ADS)

    de Santis, A.; Tozzi, R.; Wicht, J.

    2004-05-01

    Although in the past some speculations about an occurring geomagnetic field reversal were already formulated, only recently this has emerged as a really constructive hypothesis to be better investigated. From Information Content analysis of global models of the geomagnetic field and geodynamo simulations, it results that within 1000-1500 years the geomagnetic field will likely change its polarity. In this work we will present some considerations that support this possibility together with their geophysical implications.

  7. Geomagnetic excursions date early hominid migration to China

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-09-01

    Global-scale geomagnetic reversals, which are periods when the direction of Earth's magnetic field flips, leave imprints in magnetic minerals present in sediments. But so do smaller-scale, even local, changes in Earth's magnetic field direction. Paleomagnetists believe that the smaller-scale events represent “failed reversals” and refer to them as “geomagnetic excursions.” Scientists use geomagnetic excursions in sedimentary basins as markers to tie together events of Earth's history across the globe.

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

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2006-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Constable, Catherine; Parker, Robert L.

    1993-01-01

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

  10. International geomagnetic reference field 1965.0 in dipole coordinates

    NASA Technical Reports Server (NTRS)

    Mead, G. D.

    1970-01-01

    Computer program transforming spherical harmonic coefficients into arbitrarily tilted coordinate systems, tabulating coefficients of International Geomagnetic Reference Field 1965 in dipole coordinate system

  11. Classification of Regional Ionospheric Disturbances Based on Support Vector Machines

    NASA Astrophysics Data System (ADS)

    Begüm Terzi, Merve; Arikan, Feza; Arikan, Orhan; Karatay, Secil

    2016-07-01

    Ionosphere is an anisotropic, inhomogeneous, time varying and spatio-temporally dispersive medium whose parameters can be estimated almost always by using indirect measurements. Geomagnetic, gravitational, solar or seismic activities cause variations of ionosphere at various spatial and temporal scales. This complex spatio-temporal variability is challenging to be identified due to extensive scales in period, duration, amplitude and frequency of disturbances. Since geomagnetic and solar indices such as Disturbance storm time (Dst), F10.7 solar flux, Sun Spot Number (SSN), Auroral Electrojet (AE), Kp and W-index provide information about variability on a global scale, identification and classification of regional disturbances poses a challenge. The main aim of this study is to classify the regional effects of global geomagnetic storms and classify them according to their risk levels. For this purpose, Total Electron Content (TEC) estimated from GPS receivers, which is one of the major parameters of ionosphere, will be used to model the regional and local variability that differs from global activity along with solar and geomagnetic indices. In this work, for the automated classification of the regional disturbances, a classification technique based on a robust machine learning technique that have found wide spread use, Support Vector Machine (SVM) is proposed. SVM is a supervised learning model used for classification with associated learning algorithm that analyze the data and recognize patterns. In addition to performing linear classification, SVM can efficiently perform nonlinear classification by embedding data into higher dimensional feature spaces. Performance of the developed classification technique is demonstrated for midlatitude ionosphere over Anatolia using TEC estimates generated from the GPS data provided by Turkish National Permanent GPS Network (TNPGN-Active) for solar maximum year of 2011. As a result of implementing the developed classification

  12. Effects of geliogeophysical disturbances in haemorheological parameters of human

    NASA Astrophysics Data System (ADS)

    Ionova, V.; Sergeenko, N.; Sazanova, E.

    The changes of the rheological characteristics of blood at healthy people and patients with cerebrum-vascular pathology during 23 geomagnetic disturbances were studied. The analysis of dynamics of haemorheological parameters of both human groups has shown that the most of parameters are beginning statistically authentically to fall outside the normal limits already prior the beginning of the magnetic disturbance, others - per day of a beginning of disturbance. This fact specifies at an increase of variability for functional activity of blood cell in conditions of geomagnetic disturbance and allows to assume presence of direct influences of an environmental physical processes at the blood cell. The deterioration of deformation properties of erythrocytes is observed in the blood of people. The analysis of the data has resulted in occurrence of a hypothesis about appearance of instability at thrombosis-vascular part of haemostasis under influence of variation of electromagnetic field in during of magnetospheric disturbances. Such effect can be caused as direct and indirect action of an electrîmagnetic field of the Earth on the cells of blood. Haemoglobin of erythrocytes includes atoms of iron, having a deflection of the magnetic moment. In the cells, which had their erythrocytes membrane under influence of an electrîmagnetic field, had diminution of electrical mobility, that can influence the dynamics of physiological process of aggregation --disaggregation of erythrocytes in a stream of blood. Another channel of influence of geomagnetic disturbances on rheological property of blood can be connected with the action of electrîmagnetic fields through synchronization of rhythms of electromagnetic oscillations of cells of central nervous system. From the entire spectrum of an electrîmagnetic field apparent on the surface of the Earth, biologically effective factor is in a range of ultralow frequencies from 0,0001 up to 100 Ãö. The biorhythms of the brain, such as an

  13. Comparison between the effect of two geomagnetic storms with the same seasonal and daily characteristics and different intensity on the European ionosphere.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Bouza, Marta; Herraiz, Miguel; Rodríguez-Caderot, Gracía; Paparini, Claudia; Otero, Xurxo; Radicella, Sandro M.

    2016-04-01

    This work presents an analysis of the ionospheric disturbance caused by two geomagnetic storms occurred on the same day, 17th March, but one in 2013 and other in 2015. The greatest intensity of both storms occurs after sunset when geomagnetic indexes (Dst index, Kp and Ap) reached the peak values. Both geomagnetic storms can be classified as intense according to the Dst index criteria. The storm of March 17, 2015, ("St Patricḱs storm"), can be considered even "severe" because the Dst index dropped off -200nT. The solar origins of both geomagnetic storms were magnetic filament eruptions followed by Coronal Mass Ejections, CME. The ionospheric behavior has been studied through the total electron content, TEC. This parameter is obtained from RINEX files processed using the calibration technique developed by Prof. Luigi Ciraolo. RINEX files from selected GNSS stations on Europe belonging to International GPS Service, IGS, and EUREF Permanent Network, have been used. The calibration technique assumes the ionospheric thin shell model to obtain vertical total electron content (vTEC) from slant total electron content (sTEC) at the Ionospheric Pierce Point. The data were obtained in periods of the geomagnetic storms and during quite days surrounding the storms days, at 1 minute sampling. The behavior of the ionosphere during the two geomagnetic storms was similar. In both cases, a positive ionospheric storm, defined as an increase on the TEC, occurred during the main phase of the geomagnetic storms on 17th of March. These increases were followed by a negative ionospheric storm, a decreasing of TEC, in the recuperation phase. However, in the event of 2015, the positive ionospheric storm of the main phase had more intensity but the same duration than that of 2013 and for the negative ionospheric storm both, intensity and duration, were largest in 2015 than in 2013.

  14. Anomalous night-time peaks in diurnal variations of NmF2 close to the geomagnetic equator: A statistical study

    NASA Astrophysics Data System (ADS)

    Pavlov, A. V.; Pavlova, N. M.

    2007-11-01

    We present a study of anomalous night-time NmF2 peaks, ANNPs, observed by the La Paz, Natal, Djibouti, Kodaikanal, Madras, Manila, Talara, and Huancayo Jicamarca ionosonde stations close to the geomagnetic equator. It is shown for the first time that the probabilities of occurrence of the first and second ANNPs depend on the geomagnetic longitude, and there is a longitude sector close to 110° geomagnetic longitude where the first and second ANNPs occur less frequently in comparison with the longitude regions located close to and below about 34° geomagnetic longitude and close to and above about 144° geomagnetic longitude. The found frequencies of occurrence of the ANNPs increase with increasing solar activity, except of the Djibouti and Kodaikanal ionosonde stations, where the probability of the first ANNP occurrence is found to decrease with increasing solar activity from low to moderate solar activity, and except of the Natal ionosonde station, where the frequencies of occurrence of the first and second ANNPs decrease with increasing solar activity from moderate to high solar activity. We found that the occurrence probabilities of ANNPs during geomagnetically disturbed conditions are greater than those during geomagnetically quiet conditions. The ANNP probabilities are largest in summer and are lowest in winter for the La-Paz, Talara, and Huancayo Jicamarca sounders. These probabilities are lowest in summer for the Djibouti, Madras, and Manila ionosonde stations, and in spring for the Kodaikanal sounder. The maximums in the probabilities are found to be in autumn for the Djibouti, Madras, and Manila ionosonde stations, and in winter for the Kodaikanal sounder.

  15. Does a localized plasma disturbance in the ionosphere evolve to electrostatic equilibrium? Evidence to the contrary

    NASA Astrophysics Data System (ADS)

    Cosgrove, Russell B.

    2016-01-01

    Electrostatic equilibrium must be achieved through electromagnetic evolution. From an initial state with nonzero neutral wind localized along the geomagnetic field, and with all other plasma and electromagnetic perturbations initially zero, evolution progresses from plasma velocity to electric field to magnetic field, where the last step can launch an Alfvén wave that transmits the electromagnetic disturbance along geomagnetic field lines. Without the Alfvén wave the disturbance does not map along geomagnetic field lines, and there is no semblance of electrostatic equilibrium. This paradigm is essentially the traditional magnetosphere/ionosphere coupling paradigm, except addressed to smaller-scale, local ionospheric phenomena. However, Alfvén waves have not been thoroughly studied in the context of the partially ionized, collisional ionospheric plasma, and so the full effects predicted by this modeling paradigm are not known. In this work we adopt the two-fluid equations and investigate whether the ionosphere supports Alfvén-type waves that can transmit disturbances along geomagnetic field lines and perform a wave analysis of the "lumped circuit" parameters normally used to characterize the ionosphere under electrostatic equilibrium. We find that under the wave analysis (1) the Pedersen conductivity is severely modified and has a negative real part at short wavelengths; (2) the mapping distance for electric fields is significantly modified, and there is a nonnegligible wavelength along the geomagnetic field; and (3) the load admittance seen by a localized dynamo is strongly reactive, causing a phase offset between electric field and current, as compared with that when the load is electrostatic.

  16. Space-time structure of the 2003 geomagnetic jerk at Mid-Eastern Asia

    NASA Astrophysics Data System (ADS)

    Ou, Jiaming; Du, Aimin; Xu, Wenyao; Yang, Dongmei

    2015-04-01

    . Reference 1. Mandea, M., E. Bellanger, and J. L. Le Mouël (2000), A geomagnetic jerk for the end of the 20th century? Earth Planet. Sci. Lett., 183, 369-373. 2. Olsen, N. and M. Mandea (2007), Investigation of a secular variation impulse using satellite data: The 2003 geomagnetic jerk. Earth Planet. Sci. Lett., 255, 94-105. 3. Stewart, D. N. and K. A. Whaler (1992), Geomagnetic disturbance fields: an analysis of observatory monthly means. Geophys. J. Int., 108, 215-223. 4. Wardinski, I., R. Holme, S. Asari, and M. Mandea (2008), The 2003 geomagnetic jerk and its relation to the core surface flows. Earth Planet. Sci. Lett., 267, 468-481.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  18. Geomagnetic imprint of the Persani volcanism

    NASA Astrophysics Data System (ADS)

    Besutiu, Lucian; Seghedi, Ioan; Zlagnean, Luminita; Atanasiu, Ligia; Popa, Razvan-Gabriel; Pomeran, Mihai; Visan, Madalina

    2016-04-01

    The Persani small volume volcanism is located in the SE corner of the Transylvanian Depression, at the north-western edge of the intra-mountainous Brasov basin. It represents the south-easternmost segment of the Neogene-Quaternary volcanic chain of the East Carpathians. The alkaline basalt monogenetic volcanic field is partly coeval with the high-K calc-alkaline magmatism south of Harghita Mountains (1-1.6 Ma). Its eruptions post-dated the calc-alkaline volcanism in the Harghita Mountains (5.3-1.6 Ma), but pre-dated the high-K calc-alkaline emissions of Ciomadul volcano (1.0-0.03 Ma). The major volcanic forms have been mapped in previous geological surveys. Still, due to the small size of the volcanoes and large extent of tephra deposits and recent sediments, the location of some vents or other volcanic structures has been incompletely revealed. To overcome this problem, the area was subject to several near-surface geophysical investigations, including paleomagnetic research. However, due to their large-scale features, the previous geophysical surveys proved to be an inappropriate approach to the volcanological issues. Therefore, during the summers of 2014 and 2015, based on the high magnetic contrast between the volcanic rocks and the hosting sedimentary formations, a detailed ground geomagnetic survey has been designed and conducted, within central Persani volcanism area, in order to outline the presence of volcanic structures hidden beneath the overlying deposits. Additionally, information on the rock magnetic properties was also targeted by sampling and analysing several outcrops in the area. Based on the acquired data, a detailed total intensity scalar geomagnetic anomaly map was constructed by using the recent IGRF12 model. The revealed pattern of the geomagnetic field proved to be fully consistent with the direction of magnetisation previously determined on rock samples. In order to enhance the signal/noise ratio, the results were further processed by

  19. Historical variation of the geomagnetic axial dipole

    NASA Astrophysics Data System (ADS)

    Finlay, Christopher C.

    2008-09-01

    The geomagnetic axial dipole (hereinafter denoted g10) is the largest component of our planet's magnetic field. Its magnitude determines the morphology of solar-terrestrial electrical current systems and it is the most fundamental diagnostic property of the core-generated geodynamo. Elucidating past and future variations of g10(t) is consequently of central importance in geomagnetism. Previous historical geomagnetic field models, such as gufm1 of Jackson et al. [Jackson, A., Jonkers, A.R.T., Walker, M.R., 2000. Four centuries of geomagnetic secular variation from historical records. Philos. Trans. R. Soc. Lond. A 358, 957-990], used direct observations to constrain g10(t) only after 1840 A.D.; before this time a crude linear extrapolation of the post-1840 A.D. rate of change (15 nT/year) was employed. In this contribution I construct historical field models with g10(t) instead constrained from 1590 A.D. to 1840 A.D. by an archaeointensity dataset compiled by Korte et al. [Korte, M., Genevey, A., Constable, C.G., Frank, U., Schnepp, E., 2005. Continuous geomagnetic field models for the past 7 millennia. 1. A new global data compilation. Geochem. Geophys. Geosyst. 6, doi:10.1029/2004GC000800]. A range of possible linear models of the form g10(t)=g10(1840)+β(t-1840) are first explored; β=2.74±42.32 nT/year is found to explain the archaeointensity dataset with maximum likelihood, consistent with the recent findings of Gubbins et al. [Gubbins, D., Jones, A.L., Finlay, C.C., 2006. Fall in Earth's magnetic field is erratic. Science 312, 900-902]. Relaxing the linear constraint in an effort to find more physically plausible models, I find it is necessary to artificially increase the weight given to the archaeointensity data in order to obtain acceptable models. Despite satisfactorily explaining both the historical and archaeointensity data, and possessing reasonable spatial and temporal complexity, such free evolution models perform worse than the simpler linearly

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

    USGS Publications Warehouse

    Peddie, N.W.

    1992-01-01

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

  1. Comparison of polar cap electron density enhancement due to solar illumination and geomagnetic activity as measured by IMAGE/RPI

    NASA Astrophysics Data System (ADS)

    Nsumei, P.; Reinisch, B.; Song, P.; Tu, J.; Huang, X.

    2007-12-01

    Polar cap electron density (Ne) measurements made between the years 2000 - 2005 by the radio plasma imager (RPI) on board the IMAGE spacecraft are used to study the density enhancements resulting from changes in solar illumination and geomagnetic activity level. This study covers a geocentric distance, R = 1.4 - 5.0 RE and the polar cap is defined by an empirical boundary model that takes into account the dynamic nature of the location and size of the polar cap. The average polar cap electron density profile depends on geomagnetic activity level e.g., measured by the Kp index and solar illumination (solar zenith angle) at the footprints of the geomagnetic field lines. Our analysis of RPI Ne data shows that increase in geomagnetic activity leads to an enhancement in Ne. This enhancement in Ne is found to increase with altitude. At geocentric distance of R = 4.5 RE, an increase in the geomagnetic activity level from Kp < 2 to ~5 results in an Ne increase by a factor of ~5. On the other hand, a strong solar illumination control of Ne at lower altitudes, and not at higher is observed. At geocentric distance of ~ 2 RE, the average Ne is larger on the sunlit side than on the dark side by a factor of 3 - 4 both for quiet and disturbed conditions. At geocentric distance of about 2.5 RE the effects of these two factors on Ne appear to be comparable. Similar to previous polar cap density models, a functional representation of RPI Ne that takes the form of a power law is proposed. While in the previous Ne functional representations the power index is a constant, the power index in our representation of Ne distribution is found to correlate with (and hence is a function of) the Kp index and the solar zenith angle (SZA).

  2. Geomagnetically Induced Currents: Progress and Issues

    NASA Astrophysics Data System (ADS)

    Thomson, Alan

    2010-05-01

    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

  3. Long persistence effects of geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Wrenn, Gordon L.

    1990-03-01

    The identification of the physical processes which perturb the dynamic equilibrium of the charged particle populations in the terrestrial magnetosphere is investigated. A planetary index was used and it was proved that the introduction of a persistence factor for a derived index, a time weighted accumulation of recent values, gives a better correlation with an estimation of characteristic persistence times in order to establish the temporal response of observed effects in relation to available measures of geomagnetic activity. The analysis procedure was illustrated by results pertaining to ionospheric foF2, cold plasma concentration at geosynchronous orbit and ring current strength.

  4. Interplanetary magnetic field and geomagnetic Dst variations.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  5. Halo Coronal Mass Ejections and Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2009-01-01

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

  6. Geomagnetic field behaviour preceding a Superchron: new evidence for a weak Devonian geomagnetic field

    NASA Astrophysics Data System (ADS)

    Hawkins, L.; Anwar, T.; Scherbakova, V.; Biggin, A. J.; Kravchinsky, V. A.; Shatsillo, A.; Holt, J.; Pavlov, V.

    2015-12-01

    The ~50 million year transition from the peak in reversal frequency in the Middle Jurassic (~170Ma), associated with a weak geomagnetic field, to the stable and apparently strong field during the Cretaceous Normal Superchron (84-121Ma), represents a dramatic change in time-averaged geomagnetic field behaviour during the Mesozoic Era. New evidence from Siberian samples suggests there is a similar transition in geomagnetic field behaviour during the Palaeozoic, with a weak geomagnetic field in the Upper Devonian preceding the Permo-Carboniferous Superchron (262-318Ma). Both sites, the Viluy Traps and the Zharovsk complex of the Patom Margin, have seemingly reliable, published palaeomagnetic directions and new age constraints, 364.4 ± 1.7Ma (40Ar/39A) 371-377Ma (U-Pb) respectively. The samples were measured using the Thermal Thellier-Coe protocol with partial thermo-remanent magnetisation (pTRM) and tail checks and the Microwave Thellier-IZZI protocol with pTRM checks. Accepted Arai plots show positive pTRM checks, a clear relation between distinct primary directional and palaeointensity components and little to no zig-zagging. Three distinct magneto-mineralogical types were identified from SEM and rock magnetic techniques; low Ti- and intermediate Ti- titanomagnetite and possible maghemite, with mineral type affecting the success rate of samples but resulting in no significant variation in palaeointensity results. The Arai plots also commonly have a distinct two-slope concave-up shape, although non-heating, pseudo-Thellier experiments have supported this resulting from a strong overprint component rather than alteration or multi-domain effects. Results from these experiments give low site mean values between 2.3-29.9μT (Virtual Dipole Moments 4-50.6 ZAm2). The apparently periodic (~180 million years) transitions in geomagnetic field behaviour may indicate the influence of mantle convection changing heat flow across the Core Mantle Boundary.

  7. Empirical analytic transformations between geographic and corrected geomagnetic coordinates

    NASA Technical Reports Server (NTRS)

    Comfort, R. H.

    1970-01-01

    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.

  8. The use of geomagnetic field models in magnetic surveys

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  9. GPS Observation of Fast-moving Continent-size Traveling TEC Pulsations at the Start of Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Pradipta, R.; Valladares, C. E.; Doherty, P. H.

    2014-12-01

    Using network of GPS receiver stations in North and South America, we have recently observed fast-moving continent-size traveling plasma disturbances in the mapped total electron content (TEC) data. These space plasma disturbances occurred at the beginning of geomagnetic storms, immediately after the storm's suddent commencement (SSC) and prior to the appearance of large-scale traveling ionospheric disturbances (LSTIDs) from the auroral regions. More specifically, these supersize TEC perturbations were observed when the IMF Bz was oscillating between northward and southward directions. They were found to propagate zonally westward with a propagation speed of 2-3 km/s, if projected onto an ionospheric-equivalent altitude of 350 km. Based on their general characteristics and comparison with ground-based ionosonde data, we interpret these TEC pulsations as ion drift waves in the magnetosphere/plasmasphere that propagate azimuthally inside the GPS orbit.

  10. Statistical characteristics of the day-to-day variability in the geomagnetic Sq field

    NASA Astrophysics Data System (ADS)

    Chen, Gen-Xiong; Xu, Wen-Yao; Du, Ai-Min; Wu, Ying-Yan; Chen, Bo; Liu, Xiao-Can

    2007-06-01

    Day-to-day variability in the geomagnetic Sq field is studied by using the magnetic data from a meridian chain of magnetometers along 120°E longitude. The method of natural orthogonal components (NOC or eigenmode analysis) is applied to separate the Sq variation from complicated disturbances. The first eigenmode with the largest eigenvalue represents fairly well the Sq variation with a conspicuous day-to-day variability in the daily range. For the stations on the same north- or south-side of the Sq current system focus, the day-to-day variations show a positive correlation. In contrast, for the stations on the different sides of the Sq focus, they show a negative correlation, suggesting an important role of latitudinal shift of the Sq current system focus to the day-to-day variability in the Sq daily range. The Sq daily range is correlated with the magnetic indices Ap and Dst in a peculiar way: On some severe disturbed days, noticeable enhancements of the Sq are observed, implying increases in the ionospheric conductivities and/or tidal wind velocities; on other severe disturbed days, however, dramatically reduced Sq variations occur, suggesting dominant effects of the "disturbance dynamo" process.

  11. Determination of a geomagnetic storm and substorm effects on the ionospheric variability from GPS observations at high latitudes

    NASA Astrophysics Data System (ADS)

    Gómez, Luis; Ignacio Sabbione, Juan; Andrea van Zele, María; Meza, Amalia; Brunini, Claudio

    2007-06-01

    The aim of this work is to characterize the ionospheric electron content variability during a standard and simple geomagnetic storm, and substorms during it. The analysis is based on tying the geomagnetic disturbances including the signatures of the current wedge formed during the substorm expansion phase, with the variability of ionospheric vertical total electron content (VTEC) in local time; for this reason the VTEC is computed for complete geographical longitude coverage at subauroral and auroral latitudes. The study is based on the geomagnetic storm befallen on April 6 and 7, 2000 (near the equinox) and the TEC are computed from global positioning system (GPS). The main results can be divided into three groups: (a) when the geomagnetic storm starts between pre-midnight and dawn, a minimum of VTEC is recorded, lasting all the long day (ionospheric storm negative phase); also the nighttime electron content may decrease below the corresponding for quiet days; but near the 60 of geomagnetic latitude the ionization polar tongue can be observed at noon, superimposed to the negative phase; (b) computed by GPS stations placed lower than 50, when the geomagnetic storm starts between dawn and noon the VTEC recorded a positive phase, but if it starts at noon a dusk effect is recorded; those located between 50 and 60 show a sudden increase and later sudden decrease to nocturnal values, (c) when the geomagnetic storm starts between afternoon and sunset, at stations located lower than 50 a dusk effect and an ionospheric negative phase during the next day are recorded, but if the GPS stations are located at higher latitude than 50 the VTEC representation shows the nocturnal end of the ionization polar tongue. Expansion phases of substorms are shown as small VTEC variations recorded for a short time: decreases if the substorm happens between dawn and midday; enhancements during the fall of the ionospheric positive phase. From the comparison with the results obtained by other

  12. Disturbance and change in biodiversity.

    PubMed

    Dornelas, Maria

    2010-11-27

    Understanding how disturbance affects biodiversity is important for both fundamental and applied reasons. Here, I investigate how disturbances with different ecological effects change biodiversity metrics. I define three main types of disturbance effects: D disturbance (shifts in mortality rate), B disturbance (shifts in reproductive rates) and K disturbance (shifts in carrying capacity). Numerous composite disturbances can be defined including any combination of these three types of ecological effects. The consequences of D, B and K disturbances, as well as of composite DBK disturbances are examined by comparing metrics before and after a disturbance, in disturbed and undisturbed communities. I use simulations of neutral communities and examine species richness, total abundance and species abundance distributions. The patterns of change in biodiversity metrics are consistent among different types of disturbance. K disturbance has the most severe effects, followed by D disturbance, and B disturbance has nearly negligible effects. Consequences of composite DBK disturbances are more complex than any of the three types of disturbance, with unimodal relationships along a disturbance gradient arising when D, B and K are negatively correlated. Importantly, regardless of disturbance type, community isolation enhances the negative consequences and hinders the positive effects of disturbances.

  13. Science outreach and capacity building in geomagnetism and space sciences—An Indian Institute of Geomagnetism endeavor

    NASA Astrophysics Data System (ADS)

    Gawali, Praveen; Bhaskar, Ankush; Dhar, Ajay; Ramesh, Durbha Sai

    2016-05-01

    We present an overview of science outreach and capacity building activities at the Indian Institute of Geomagnetism (IIG) against the backdrop of a long history of geomagnetic studies. We also present the future plans of the institute for strengthening these activities.

  14. Forecasts of solar and geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Joselyn, Joann

    1987-01-01

    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.

  15. Geomagnetic excursions reflect an aborted polarity state

    NASA Astrophysics Data System (ADS)

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

    2008-10-01

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

  16. Solar Wind Charge Exchange During Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  17. Atmospheric helium and geomagnetic field reversals.

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  18. Indicators: Human Disturbance

    EPA Pesticide Factsheets

    Human disturbance is a measure of the vulnerability of aquatic resources to a variety of harmful human activities such as tree removal, road building, construction near shorelines/streambanks, and artificial hardening of lakeshores with retaining walls.

  19. Influence of Different Solar Drivers on the Winds in the Middle Atmosphere and on Geomagnetic Disturbances

    DTIC Science & Technology

    2007-05-18

    QBO Easterly; the legend is like in Fig.11. Magnetic clouds Fig.16 presents NAM and SAM index relative to zhe days with magnetic clouds. The...Oxford, 1964. Tsurutani, B. T., Lee, Y. T., Gonzalez, W. D., Tang , F. Great magnetic storms.Geophysical Research Letters (ISSN 0094-8276), vol. 19

  20. Use of Interplanetary Radio Scintillation Power Spectra in Predicting Geomagnetic Disturbances.

    DTIC Science & Technology

    1977-10-31

    COCOA -Cross array at 34.3 MHz located at Clark Lake Radio Observatory near Borrego Springs, California and synoptic data on 33 sources were reduced to...yield scintillation index (band-pass integrated IPS power) for each source. In 1976, COCOA -Cross observations at 34.3 MHz were supplemented by 38 MHz

  1. Partitioning of Electromagnetic Energy Inputs to the Thermosphere during Geomagnetic Disturbances

    DTIC Science & Technology

    2012-06-01

    new theory that relates neutral density cell structure to divergences of the ⃗ ⃗⃗ force. At E-region altitudes these divergences arise because of...thermosphere. Solar wind energy is transferred indirectly through an interaction with Earth’s magnetic field that gives rise to an electromagnetic dynamo ... Dynamo energy flowing into the thermosphere is mediated by the ionosphere. Unlike solar EUV radiation to which the thermosphere responds passively

  2. Behavior of high-latitude irregularities during geomagnetic disturbances. Environmental research papers

    SciTech Connect

    Houminer, Z.; Aarons, J.

    1980-06-24

    Scintillation observations of VHF and UHF transmissions from geostationary satellites at Goose Bay have been used to study the average characteristics of the high latitude irregularity region. The paper describes the average time development and mean diurnal pattern of irregularities during 58 magnetic storms in 1971-1976. The diurnal variation at Goose Bay shows two peaks of scintillation activity. One peak occurs during the afternoon hours, while the second occurs during the night. The average diurnal pattern is independent of type of storm. diurnal and seasonal effects appear only in the first day of storm commencement and not in the following days which show a very similar diurnal picture. (Author)

  3. Pre Earthquake Phenomena in Phase Velocities and Gradients of ULF Geomagnetic Disturbances

    NASA Astrophysics Data System (ADS)

    Raspopov, O.; Kopytenko, Y.; Ismaguilov, V.; Hattori, K.; Hayakawa, M.

    2003-12-01

    Tree high-sensitive three-component torsion magnetometers MVC-2DS were operating in Japan before and during a seismic active period started 26.06.2000. A seismic active region was situated to the southeast from Izu peninsula. The strongest seismic shock with magnitude MS=6.4 had taken place 01.07.2000 under a sea bottom at a distance ~85 km from the magnetic stations. The magnetometers were installed at the Izu peninsula in tops of a triangle at a distance 4-6 km from each other. This configuration of the magnetic stations allows determining of gradient and phase velocity vectors along the earth's surface using a phase-gradient method. The vectors of the gradient are usually directed to a source of the ULF EM waves, the vectors of the phase velocity - from the source. A time evolution of the phase velocity and gradient values of the pulsations with periods T=2-512 s (data were preliminary filtered by narrow pass-band filters) was investigated before and during the seismic active period (from 1.02 to 25.07.2000). An increasing of the phase velocity and gradient values was observed ~1.5 months before first seismic foreshock. The greatest values in Z component were reached close to the moment of the EQ. The increasing of the phase velocity values was observed only in direction from the future seismic activity region. There was no change of the phase velocities in the opposite direction. A sharp increasing of the gradients was distinctly seen ~2-3 days before the seismic shocks with Ms>6. The effect was most clearly observed in the short-period pulsations in the total horizontal component. A new direction of the gradient vectors in the total horizontal component aroused 2-3 weeks before the seismic activity beginning - just the direction to the future seismic activity region. The phase velocity vectors shown a new direction (just the direction from the future seismic activity region) in the total horizontal component the same 2-3 weeks before the seismic activity start. The phase velocity and gradient vectors in Z component were mostly connected with the seawater induction currents ("sea coast" effect) and only during the seismic active period the vector directions were connected with ULF EM sources situated in the seismic active region. A comparison of the ULF magnetic field variations at the Kakioka magnetic station, located ~200 km to the northwest from the magnetic stations, with the gradient values at the Izu peninsula shows a low correlation between a magnetic activity and the time evolution of the magnetic pulsation gradients.We suppose that the gradients and phase velocities features observed before the seismic activity start is probably connected with an arising of a local geoelectric anomaly connected with the future seismic region. The increasing of the gradients just before the strong seismic shocks is probably connected with the ULF EM emissions exited in the seismic activity region situated in the Earth's crust.

  4. Disturbances of the Low Latitude Ionosphere During Extremes of Geomagnetic Activity

    DTIC Science & Technology

    2003-09-30

    Boston University, we have made a coordinated series of observations at Arequipa (Peru) near the magnetic equator and at Tucuman (Argentina) at 14o...conditions were found to be more rapid at the anomaly site (Argentina) than at the site on the magnetic equator (Peru). These results from Arequipa and...view of the three southern hemisphere imaging systems shown in Figure 1 (a), Arequipa , Tucuman and El Leoncito, in order to extend the latitudinal

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

    NASA Astrophysics Data System (ADS)

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

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

  6. Response of the thermosphere and ionosphere to geomagnetic storms

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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 heating raises the temperature of the upper thermosphere and ion drag drives high-velocity neutral winds. The heat source drives a global wind surge, from both polar regions, which propagates to low latitudes and into the opposite hemisphere. The surge has the character of a large-scale gravity wave with a phase speed of about 600 m/s. Behind the surge a global circulation of magnitude 100 m/s is established at middle latitudes, indicating that the wave and the onset of global circulation are manifestations of the same phenomena. A dominant feature of the response is the penetration of the surge into the opposite hemisphere where it drives poleward winds for a few hours. The global wind surge has a preference for the night sector and for the longitude of the magnetic pole and therefore depends on the UT start time of the storm. A second phase of the meridional circulation develops after the wave interaction but is also restricted, in this case by the buildup of zonal winds via the Coriolis interaction. Conservation of angular momentum may limit the buildup of zonal wind in extreme cases. The divergent wind field drives upwelling and composition change on both height and pressure surfaces. The composition bulge responds to both the background and the storm-induced horizontal winds; it does not simply rotate with Earth. During the storm the disturbance wind modulates the location of the bulge; during the recovery the background winds induce a diurnal variation in its position. Equatorward winds in sunlight produce positive ionospheric changes during the main driving

  7. Studies on the Geomagnetic Induction Vectors of China

    NASA Astrophysics Data System (ADS)

    Wang, Qiao; Zhang, Huiqian; Huang, Qinghua

    2016-04-01

    In this study, the geomagnetic data of 16 stations, near 6 years for most, provided by the National Geomagnetic Center of China, were used to study on the geomagnetic induction vectors. The stations cover the whole North China and part of southwestern China, both of which has a complicate geological and tectonic background. This study will not only advance the understanding of regional tectonic variations, but also provide some suggestions on the construction for geomagnetic observation network of earthquake monitoring. The time series of geomagnetic induction vectors were obtained by the robust estimation method, which has been verified and compared with the ordinary least square and the weighted square method. A principle of selecting a specified period's results from the robust estimation method was defined. Then, the results with the period of 640s for all stations were selected by this principle. The long-term trends (more than six months at least) within the time series were extracted by the Fourier harmonic analysis. Consistent phase variations exist for most stations within a similar tectonic background. About one-month period variations in the most stations' results after removing the long-term trends were found. Spectrum analysis for the results and geomagnetic activity index showed that those phenomena may relate to the period of the global geomagnetic activity. A preference azimuth of the geomagnetic induction vectors was found in each station by statistical analysis on the time series. It pointed out the possible relatively high conductivity structures. Exactly, geomagnetic vectors of BJI, JIH, LYH and TAY station, which surround the basin of North China, suggested a relatively higher conductivity layer; that of stations around the Erdos block suggested a complicated structure. Three-dimension inversion by ModEM verifies our results.

  8. Geomagnetically induced currents in the Irish power network during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Blake, Seán. P.; Gallagher, Peter T.; McCauley, Joe; Jones, Alan G.; Hogg, Colin; Campanyà, Joan; Beggan, Ciarán. D.; Thomson, Alan W. P.; Kelly, Gemma S.; Bell, David

    2016-12-01

    Geomagnetically induced currents (GICs) are a well-known terrestrial space weather hazard. They occur in power transmission networks and are known to have adverse effects in both high-latitude and midlatitude countries. Here we study GICs in the Irish power transmission network (geomagnetic latitude 54.7-58.5°N) during five geomagnetic storms (6-7 March 2016, 20-21 December 2015, 17-18 March 2015, 29-31 October 2003, and 13-14 March 1989). We simulate electric fields using a plane wave method together with two ground resistivity models, one of which is derived from magnetotelluric measurements (magnetotelluric (MT) model). We then calculate GICs in the 220, 275, and 400 kV transmission network. During the largest of the storm periods studied, the peak electric field was calculated to be as large as 3.8 V km-1, with associated GICs of up to 23 A using our MT model. Using our homogenous resistivity model, those peak values were 1.46 V km-1 and 25.8 A. We find that three 400 and 275 kV substations are the most likely locations for the Irish transformers to experience large GICs.

  9. Initial geomagnetic field model from MAGSAT

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  10. Stochastic resonance in geomagnetic polarity reversals.

    PubMed

    Consolini, Giuseppe; De Michelis, Paola

    2003-02-07

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

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

    PubMed

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

    2001-01-01

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

  12. Equatorial All Sky Imager Images from the Seychelles during the March 17th, 2015 geomagnetic storm.

    NASA Astrophysics Data System (ADS)

    Curtis, B.

    2015-12-01

    An all sky imager was installed in the Seychelles earlier this year. The Seychelles islands are located northeast of Madagascar and east of Somalia in the equatorial Indian Ocean. The all sky imager is located on the island of Mahe (4.6667°S, 55.4667°E geographic), (10.55°S, 127.07°E geomagnetic), with filters of 557.7, 620.0, 630.0, 765.0 and 777.4 nm. Images with a 90 second exposure from Seychelles in 777.4nm and 630.0nm from the night before and night of the March 17th geomagnetic storm are discussed in comparison to solar wind measurements at ACE and the disturbance storm time (Dst) index. These images show line-of-sight intensities of photons received dependent on each filters wavelength. A time series of these images sometimes will show the movement of relatively dark areas, or depletions, in each emission. The depletion regions are known to cause scintillation in GPS signals. The direction and speed of movement of these depletions are related to changes observed in the solar wind.

  13. Geomagnetism and paleomagnetism 1979-1983

    NASA Astrophysics Data System (ADS)

    Fuller, M.

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

  14. Forecasting geomagnetic activities from the Boyle Index

    NASA Astrophysics Data System (ADS)

    Bala, R.; Reiff, P. H.

    2010-12-01

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

  15. Sleep disturbances in Parkinsonism.

    PubMed

    Askenasy, J J M

    2003-02-01

    The present article is meant to suggest an approach to the guidelines for the therapy of sleep disturbances in Parkinson's Disease (PD) patients.The factors affecting the quality of life in PD patients are depression, sleep disturbances and dependence. A large review of the literature on sleep disturbances in PD patients, provided the basis for the following classification of the sleep-arousal disturbances in PD patients. We suggest a model based on 3 steps in the treatment of sleep disturbances in PD patients. This model allowing the patient, the spouse or the caregiver a quiet sleep at night, may postpone the retirement and the institutionalization of the PD patient. I. Correct diagnosis of sleep disorders based on detailed anamnesis of the patient and of the spouse or of the caregiver. One week recording on a symptom diary (log) by the patient or the caregiver. Correct diagnosis of sleep disorders co morbidities. Selection of the most appropriate sleep test among: polysomnography (PSG), multiple sleep latency test (MSLT), multiple wake latency test (MWLT), Epworth Sleepiness Scale, actigraphy or video-PSG. II. The nonspecific therapeutic approach consists in: a) Checking the sleep effect on motor performance, is it beneficial, worse or neutral. b) Psycho-physical assistance. c) Dopaminergic adjustment is necessary owing to the progression of the nigrostriatal degeneration and the increased sensitivity of the terminals, which alter the normal modulator mechanisms of the motor centers in PD patients. Among the many neurotransmitters of the nigro-striatal pathway one can distinguish two with a major influence on REM and NonREM sleep. REM sleep corresponds to an increased cholinergic receptor activity and a decreased dopaminergic activity. This is the reason why REM sleep deprivation by suppressing cholinergic receptor activity ameliorates PD motor symptoms. L-Dopa and its agonists by suppressing cholinergic receptors suppress REM sleep. The permanent adjustment

  16. An Impending geomagnetic transition? Hints from the past.

    NASA Astrophysics Data System (ADS)

    Laj, Carlo; Kissel, Catherine

    2015-10-01

    The rapid decrease of the geomagnetic field intensity in the last centuries has led to speculations that an attempt to a reversal or an excursion might be under way. Here we investigate this hypothesis by examining past records of geomagnetic field intensity obtained from sedimentary cores and from the study of cosmogenic nuclides. The selected records describe geomagnetic changes with an unprecedented temporal resolution between 20 and 75 kyr B.P. We find that some aspects of the present-day geomagnetic field have some similarities with those documented for the Laschamp excursion 41 kyr ago. Under the assumption that the dynamo processes for an eventual future reversal or excursion would be similar to those of the Laschamp excursion, we tentatively suggest that, whilst irreversible processes that will drive the geodynamo into a polarity change may have already started, a reversal or an excursion should not be expected before 500 to 1000 years.

  17. Interplanetary magnetic sector polarity inferred from polar geomagnetic field observations

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

    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.

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

    USGS Publications Warehouse

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

    1987-01-01

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

  19. Geomagnetic Variations of Near-polar Regions and Human Health

    NASA Astrophysics Data System (ADS)

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

    In polar region geomagnetic variations play active role to non-linear tectonic processes. This analysis is based on spatial-time spectral representation of geomagnetic variation and wave migration transformation. Many perturbations in electromagnetic fields may because by external factors (e.g. magnetic storms, ionosphere anomalies and other phenomena related to solar activity) "trigging" tectonic processes but having no direct relation to the processes of their preparation. Geophysical processes are responsible for perturbations in Earth's rotation and orientation on wide range of time-scale, from less than a day of millions of years. The geological structure of some sites of Earth's crust promotes occurrence of wave guides a number of geophysical fields (acoustic, seismic, electromagnetic), usually of transportation of acoustic, seismic, electromagnetic energy in Earth's crust are coincide spatially. During last 250 mln years Arctic Segment has been developing as an autonomous region with circumpolar zonality of geomagnetic fields, and mass - and-energy transfer in its bowlers as well as shitting of lithospheric plates and expansion of ocean are caused by rotation forces under of expanding planet. The dynamic structure of the geomagnetic variations may be characteriz ed by the variations of the order-chaos state. The order manifest itself in the rhythmic change of the medium state. Analysis of amplitude and phase of geomagnetic variations can be information on ecological state of regions. Geomagnetic variations is intrincically a multiscale process in time and space. One of the most important features of geomagnetic variations is multicyclic character, whish predetermined both extent and character of geomagnetic show, and specific features. Recently, there are collected many facts, show dependence between the processes in the Earth's biosphere, the elements of it, gelio- geo- physical and meteorological factors. The recent experimental data gives us opportunity

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Heirtzler, J. R.

    1999-01-01

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

  2. The ROSCOE Manual. Volume 15. ambient geomagnetic field

    DTIC Science & Technology

    1975-06-13

    Continue on reverse side it necessary and identify by bloc;, number) ROSCOE\\ ~ Ambient Geomagnetic Model .3 ABSTRACT fC.-ntinue on re.erse side if...necesAary end idrnttlyhr block number) A preliminary model of the ambient geomagnetic field has been adopted for use in ROSCOE. The model fits a locally...presented derivations, flow d’,%rams, Fortran listings, and a test problem and evaluation. The model is found to he both fast and accurate. ream DD I

  3. New idea of geomagnetic monitoring through ENA detection from the International Space Station: ENAMISS project

    NASA Astrophysics Data System (ADS)

    Milillo, Anna; De Angelis, Elisabetta; Orsini, Stefano; Rubini, Alda; Evangelista, Yuri; Mura, Alessandro; Rispoli, Rosanna; Vertolli, Nello; Carrubba, Elisa; Donati, Alessandro; Di Lellis, Andrea Maria; Plainaki, Christina; Lazzarotto, Francesco

    2016-04-01

    , these latter having relevance in electric orbit raising, will be developed and made available for the satellite operators. Finally, a continuous global monitoring of the geomagnetic disturbances in the inner magnetosphere via ENA imaging from the ISS could represent an innovative Space Weather data product for European infrastructures dedicated to geomagnetic data distribution and now-cast services as for example ESPAS and the Space Situational Awareness (SSA) program of ESA.

  4. Pearl-type micropulsations at mid-latitude; their relation to whistlers, solar and geomagnetic activity as well as ionospheric absorption

    NASA Astrophysics Data System (ADS)

    Märcz, F.; Verő, J.

    2002-02-01

    The occurrence of pearl-type (Pc 1) micropulsations recorded at the mid-latitude station Nagycenk (Hungary) during a half solar cycle showed a quite regular variation on this long time scale. Around solar activity maximum, the number of days with Pc 1 occurrence was rather low, while it began to increase during medium solar activity rising to a maximum around solar activity minimum. Pc 1 pulsations have been analyzed in relation to further parameters and on a shorter time scale, too. Based on data of 2 years with maximum Pc 1 occurrence (around solar activity minimum in 1985 and 1986), a seasonal variation was also found. Additionally, it was confirmed that pearl-type micropulsations might frequently occur, on and after days, with geomagnetic disturbances. At Nagycenk, the selected geomagnetic disturbances were generally associated with an increased ionospheric absorption of radio waves caused by enhanced ionization due to particle precipitation from the magnetosphere into the lower ionosphere. Whistler observations carried out at Panska Veš (a station in the Czech Republic) showed a significant whistler activity connected with these geomagnetic disturbances, however, no after-effect appeared in whistler activity. One of the main goals of the present study was to find a relationship between Pc 1 pulsations and whistlers. Results revealing an increased whistler activity associated with Pc 1 occurrences confirm our previous findings rather convincingly. The latter ones hinted at the probability that certain magnetospheric configurations, e.g. geomagnetic field line shells and whistler ducts are closely connected, as similar positions of the two structures were found within the magnetosphere when characteristics of Pc 3 pulsations and whistlers were analyzed.

  5. Influence of geomagnetic activity and atmospheric pressure in hypertensive adults.

    PubMed

    Azcárate, T; Mendoza, B

    2017-03-30

    We performed a study of the systolic and diastolic arterial blood pressure behavior under natural variables such as the atmospheric pressure and the horizontal geomagnetic field component. We worked with a group of eight adult hypertensive volunteers, four men and four women, with ages between 18 and 27 years in Mexico City during a geomagnetic storm in 2014. The data was divided by gender, age, and day/night cycle. We studied the time series using three methods: correlations, bivariate analysis, and superposed epoch (within a window of 2 days around the day of occurrence of a geomagnetic storm) analysis, between the systolic and diastolic blood pressure and the natural variables. The correlation analysis indicated a correlation between the systolic and diastolic blood pressure and the atmospheric pressure and the horizontal geomagnetic field component, being the largest during the night. Furthermore, the correlation and bivariate analyses showed that the largest correlations are between the systolic and diastolic blood pressure and the horizontal geomagnetic field component. Finally, the superposed epoch analysis showed that the largest number of significant changes in the blood pressure under the influence of geomagnetic field occurred in the systolic blood pressure for men.

  6. Are migrating raptors guided by a geomagnetic compass?

    USGS Publications Warehouse

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

    2006-01-01

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

  7. Globally strong geomagnetic field intensity circa 3000 years ago

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  8. Interhemispheric propagation and interactions of auroral traveling ionospheric disturbances near the equator

    NASA Astrophysics Data System (ADS)

    Pradipta, Rezy; Valladares, Cesar E.; Carter, Brett A.; Doherty, Patricia H.

    2016-03-01

    We present the results of our GPS total electron content and ionosonde observations of large-scale traveling ionospheric disturbances (LSTIDs) during the 26 September 2011 geomagnetic storm. We analyzed the propagation characteristics of these LSTIDs from the auroral zones all the way to the equatorial region and studied how the auroral LSTIDs from opposite hemispheres interact/interfere near the geomagnetic equator. We found an overall propagation speed of ˜700 m/s for these LSTIDs and that the resultant amplitude of the LSTID interference pattern actually far exceeded the sum of individual amplitudes of the incoming LSTIDs from the immediate vicinity of the interference zone. We suspect that this peculiar intensification of auroral LSTIDs around the geomagnetic equator is facilitated by the significantly higher ceiling/canopy of the ionospheric plasma layer there. Normally, acoustic-gravity waves (AGWs) that leak upward (and thus increase in amplitude) would find a negligible level of plasma density at the topside ionosphere. However, the tip of the equatorial fountain at the geomagnetic equator constitutes a significant amount of plasma at a topside-equivalent altitude. The combination of increased AGW amplitudes and a higher plasma density at such altitude would therefore result in higher-amplitude LSTIDs in this particular region, as demonstrated in our observations and analysis.

  9. A Quaternary Geomagnetic Instability Time Scale

    NASA Astrophysics Data System (ADS)

    Singer, B. S.

    2013-12-01

    Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought

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

    NASA Astrophysics Data System (ADS)

    Yoshida, A.

    2008-12-01

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

  11. Possible Linkage between Geomagnetic Field, Temperature and Monsoon: Implication of High-Resolution Magnetic and Climatic Data from a Sediment Core in Osaka Bay, Japan

    NASA Astrophysics Data System (ADS)

    Kitaba, I.; Hyodo, M.; Katoh, S.; Dettman, D. L.; Sato, H.

    2013-12-01

    Observed correlation between galactic cosmic ray (CR) flux and cloud cover suggests that variations in geomagnetic field intensity could change climate through modulation of CR flux. Kitaba et al. (2013) reported a pollen-based climate cooling that coincided with a large decrease in field intensity during the Matuyama-Brunhes and Lower Jaramillo geomagnetic polarity reversals using a sediment core from Osaka Bay, Japan. The cooling event is not attributed to orbital forcing, but to the geomagnetic field intensity variation through modulation of CR flux. If the geomagnetic field intensity disturbs global heat balance, it may further affect monsoon and/or precipitation. Our pollen-based climate data show that during the cooling the difference in mean temperature between the warmest and coldest months (indicator of land-ocean temperature gradient) increased, and the summer precipitation (indicator of summer monsoon intensity) decreased. Assuming a simple model that the monsoon is driven by the land-ocean temperature gradient, the cooling effect would be larger over the land than the sea.

  12. Probing geomagnetic storm-driven magnetosphere-ionosphere dynamics in D-region via propagation characteristics of very low frequency radio signals

    NASA Astrophysics Data System (ADS)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip K.; Ogunmodimu, Olugbenga

    2016-07-01

    The amplitude and phase of VLF/LF radio signals are sensitive to changes in electrical conductivity of the lower ionosphere which imprints its signature on the Earth-ionosphere waveguide. This characteristic makes it useful in studying sudden ionospheric disturbances, especially those related to prompt X-ray flux output from solar flares and gamma ray bursts (GRBs). However, strong geomagnetic disturbance and storm conditions are known to produce large and global ionospheric disturbances, which can significantly affect VLF radio propagation in the D region of the ionosphere. In this paper, using the data of three propagation paths at mid-latitudes (40-54°), we analyse the trend in variation of aspects of VLF diurnal signal under varying solar and geomagnetic space environmental conditions in order to identify possible geomagnetic footprints on the D region characteristics. We found that the trend of variations generally reflected the prevailing space weather conditions in various time scales. In particular, the 'dipping' of mid-day signal amplitude peak (MDP) occurs after significant geomagnetic perturbed or storm conditions in the time scale of 1-2 days. The mean signal amplitude before sunrise (MBSR) and mean signal amplitude after sunset (MASS) also exhibit storm-induced dipping, but they appear to be influenced by event's exact occurrence time and the highly variable conditions of dusk-to-dawn ionosphere. We also observed few cases of the signals rise (e.g., MDP, MBSR or MASS) following a significant geomagnetic event. This effect may be related to storms associated phenomena or effects arising from sources other than solar origin. The magnitude of induced dipping (or rise) significantly depends on the intensity and duration of event(s), as well as the propagation path of the signal. The post-storm day signal (following a main event, with lesser or significantly reduced geomagnetic activity) exhibited a tendency of recovery to pre-storm day level. In the

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

    USGS Publications Warehouse

    Campbell, W.H.

    1996-01-01

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

  14. Geomagnetic Field -- From Paleomagnetism to Dynamo Theory

    NASA Astrophysics Data System (ADS)

    Kono, M.

    2008-05-01

    Since 1995, self-consistent models of the geodynamo became available. There are certain problems, but some of these models have shown behaviors quite similar to those observed by paleomagnetism, including polarity reversals (Kono and Roberts, 2002). There is thus a hope that the combination of paleomagnetism and dynamo theory may provide us a very comprehensive understanding of the geomagnetic field. In this paper, I will try to highlight the possibilities and limitations in such studies. From satellite observations, it was shown that the power of the magnetic field contained in each degree is nearly the same if measured at the core-mantle boundary (CMB). The core field can be seen only to degree 13 or 14 where the field power is about (10 nT)2. Beyond that, the crustal magnetization dominates and the core signal is lost. The value of 10 nT is far larger than the accuracy of the present-day instruments, but much smaller than the resolution obtainable by paleomagnetic observations. We may safely assume that the error in paleomagnetic measurements (in direction) is of the order of 10 degrees. This error corresponds to the resolution of about 1/5. The relative powers of the low degree terms in the magnetic field at the surface are 1.0, 0.033, 0.019, 0.0055 (Langel and Estes, 1982). This means that only the degrees 1 to 3 terms may be distinguished by paleomagnetic data. From the combination of dipole, quadrupole, and octupole, what we can deduce about the fundamental properties of the geomagnetic field? Here are some of the possibilities, which may give important clues when we compare with dynamo simulation results. (1) The current dipole power is several times larger than the value expected from the trend line produced by degrees 2--13. Is this a persistent feature or transient? (2) In PSV analysis, the angular standard deviation increases with latitude. Kono and Tanaka (1995) showed that it is possible only if the (2,1) (degree, order) or (3,2) term is very large

  15. Recognition of disturbances with specified morphology in time series: Part 2. Spikes on 1-s magnetograms

    NASA Astrophysics Data System (ADS)

    Soloviev, A. A.; Agayan, S. M.; Gvishiani, A. D.; Bogoutdinov, Sh. R.; Chulliat, A.

    2012-05-01

    Preliminary magnetograms contain different types of temporal anthropogenic disturbances: spikes, baseline jumps, drifts, etc. These disturbances should be identified and filtered out during the preprocessing of the preliminary records for the definitive data. As of now, at the geomagnetic observatories, such filtering is carried out manually. Most of the disturbances in the records sampled every second are spikes, which are much more abundant than those on the magnetograms sampled every minute. Another important feature of the 1-s magnetograms is the presence of a plenty of specific disturbances caused by short-period geomagnetic pulsations, which must be retained in the definitive records. Thus, creating an instrument for formalized and unified recognition of spikes on the preliminary 1-s magnetograms would largely solve the problem of labor-consuming manual preprocessing of the magnetic records. In the context of this idea, in the present paper, we focus on recognition of the spikes on the 1-s magnetograms as a key point of the problem. We describe here the new algorithm of pattern recognition, SPs, which is capable of automatically identifying the spikes on the 1-s magnetograms with a low probability of missed events and false alarms. The algorithm was verified on the real magnetic data recorded at the French observatory located on Easter Island in the Pacific.

  16. Periodic substorm activity in the geomagnetic tail

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  17. Geomagnetism during solar cycle 23: Characteristics.

    PubMed

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

    2013-05-01

    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.

  18. The Livingston Island Geomagnetic and Ionospheric Observatory

    NASA Astrophysics Data System (ADS)

    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

    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.

  19. Historical Data for Geomagnetic Field Modelling

    NASA Technical Reports Server (NTRS)

    Jackson, Andrew

    1992-01-01

    Described here are the various types of historical data (by which we mean actual measurements of the field taken in the past) which are available for geomagnetic field modelling, concentrating exclusively on observations made prior to the 20th century. These data take quite diverse forms, being derived from voyages of discovery or scientific expeditions, from surveys on land, or from observatories after the formation of the Gottingen Magnetic Union. Toward the latter part of the 19th Century, declination was measured quite regularly by various naval vessels for the purpose of constructing charts. Prior to the invention of a method for measuring field intensities by Gauss in 1832, all measurements were of declination or inclination. During the 19th Century over 40,000 observations are available in one year (the first International Polar Year 1882-83). Prior to 1800 there are only of the order of 12,000 measurements. We discuss measurement methods and the types of instruments used, and focus on specific problems which have been noted, such as those associated with the measurement of intensity on iron ships in the late 19th Century.

  20. Geomagnetism during solar cycle 23: Characteristics

    PubMed Central

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

    2012-01-01

    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

  1. Major Geomagnetic Storms in Solar Cycle 24

    NASA Astrophysics Data System (ADS)

    Zheng, Y.

    2013-12-01

    Solar Cycle 24 has produced 11 major geomagnetic storms (where Dstmin < -100 nT) with three in 2011, six in 2012 and two in 2013 (as of 7 August 2013). Detailed analysis of each event will be given in terms of its solar driver(s): CME, coronal hole high speed solar wind stream (HSS), multiple CMEs or interactions between CME and HSS. While some of these storms are associated with a fast and wide CME, the few cases involving slow or common CMEs and interactions with HSS are particularly interesting. These events pose great challenges for accurate space weather forecasting, since operationally the slower or average CMEs tend to receive less attention and are sometimes overlooked altogether. The characteristics of such challenging, not-so-fast yet geoeffective CME events (such as their coronal signatures and interactions with surrounding solar wind structure(s), etc) will be examined in detail, with the goal of extracting common and telltale features, if any, of these CMEs that distinguish them from CMEs in a similar category.

  2. Low-dimensional analysis of geomagnetic reversals

    NASA Astrophysics Data System (ADS)

    Morzfeld, M.; Fournier, A.; Hulot, G.

    2015-12-01

    Low-dimensional models for Earth's magnetic dipole have attracted attention recently because they may be a powerful tool to study the dominant dynamics over geological time-scales, where direct numerical simulation remains challenging. We investigate the extent to which several low-dimensional models can explain the Earth's dipole dynamics by comparing them to the signed relative paleointensity over the past 2 million years. Our comparisons of models and data are done by Bayesian statistics, which allows us to incorporate nonlinearity and uncertainty into the computations. The comparison, or data assimilation, reveals the strengths and weaknesses of each low-dimensional model and suggests improvements to the low-dimensional models. We also investigate if low-dimensional models can predict dipole reversals by performing extensive numerical experiments, and by hind-casting the Laschamp event, the Bruhnes-Matuyama reversal, as well as four other reversals documented over the past two million years. Our analysis stresses the need for models of geomagnetic reversals to faithfully account for the full spectrum of variability of paleomagnetic intensity.

  3. 300 Area Disturbance Report

    SciTech Connect

    LL Hale; MK Wright; NA Cadoret

    1999-01-07

    The objective of this study was to define areas of previous disturbance in the 300 Area of the U.S. Department of Energy (DOE) Hanford Site to eliminate these areas from the cultural resource review process, reduce cultural resource monitoring costs, and allow cultural resource specialists to focus on areas where subsurface disturbance is minimal or nonexistent. Research into available sources suggests that impacts from excavations have been significant wherever the following construction activities have occurred: building basements and pits, waste ponds, burial grounds, trenches, installation of subsurface pipelines, power poles, water hydrants, and well construction. Beyond the areas just mentioned, substrates in the' 300 Area consist of a complex, multidimen- sional mosaic composed of undisturbed stratigraphy, backfill, and disturbed sediments; Four Geographic Information System (GIS) maps were created to display known areas of disturbance in the 300 Area. These maps contain information gleaned from a variety of sources, but the primary sources include the Hanford GIS database system, engineer drawings, and historic maps. In addition to these maps, several assumptions can be made about areas of disturbance in the 300 Area as a result of this study: o o Buried pipelines are not always located where they are mapped. As a result, cultural resource monitors or specialists should not depend on maps depicting subsurface pipelines for accurate locations of previous disturbance. Temporary roads built in the early 1940s were placed on layers of sand and gravel 8 to 12 in. thick. Given this information, it is likely that substrates beneath these early roads are only minimally disturbed. Building foundations ranged from concrete slabs no more than 6 to 8 in. thick to deeply excavated pits and basements. Buildings constructed with slab foundations are more numerous than may be expected, and minimally disturbed substrates may be expected in these locations. Historic black

  4. Waveguide disturbance detection method

    DOEpatents

    Korneev, Valeri A.; Nihei, Kurt T.; Myer, Larry R.

    2000-01-01

    A method for detection of a disturbance in a waveguide comprising transmitting a wavefield having symmetric and antisymmetric components from a horizontally and/or vertically polarized source and/or pressure source disposed symmetrically with respect to the longitudinal central axis of the waveguide at one end of the waveguide, recording the horizontal and/or vertical component or a pressure of the wavefield with a vertical array of receivers disposed at the opposite end of the waveguide, separating the wavenumber transform of the wavefield into the symmetric and antisymmetric components, integrating the symmetric and antisymmetric components over a broad frequency range, and comparing the magnitude of the symmetric components and the antisymmetric components to an expected magnitude for the symmetric components and the antisymmetric components for a waveguide of uniform thickness and properties thereby determining whether or not a disturbance is present inside the waveguide.

  5. Atmospheric Disturbance Environment Definition

    NASA Technical Reports Server (NTRS)

    Tank, William G.

    1994-01-01

    Traditionally, the application of atmospheric disturbance data to airplane design problems has been the domain of the structures engineer. The primary concern in this case is the design of structural components sufficient to handle transient loads induced by the most severe atmospheric "gusts" that might be encountered. The concern has resulted in a considerable body of high altitude gust acceleration data obtained with VGH recorders (airplane velocity, V, vertical acceleration, G, altitude, H) on high-flying airplanes like the U-2 (Ehernberger and Love, 1975). However, the propulsion system designer is less concerned with the accelerations of the airplane than he is with the airflow entering the system's inlet. When the airplane encounters atmospheric turbulence it responds with transient fluctuations in pitch, yaw, and roll angles. These transients, together with fluctuations in the free-stream temperature and pressure will disrupt the total pressure, temperature, Mach number and angularity of the inlet flow. For the mixed compression inlet, the result is a disturbed throat Mach number and/or shock position, and in extreme cases an inlet unstart can occur (cf. Section 2.1). Interest in the effects of inlet unstart on the vehicle dynamics of large, supersonic airplanes is not new. Results published by NASA in 1962 of wind tunnel studies of the problem were used in support of the United States Supersonic Transport program (SST) (White, at aI, 1963). Such studies continued into the late 1970's. However, in spite of such interest, there never was developed an atmospheric disturbance database for inlet unstart analysis to compare with that available for the structures load analysis. Missing were data for the free-stream temperature and pressure disturbances that also contribute to the unStart problem.

  6. Global Scale Solar Disturbances

    NASA Astrophysics Data System (ADS)

    Title, A. M.; Schrijver, C. J.; DeRosa, M. L.

    2013-12-01

    The combination of the STEREO and SDO missions have allowed for the first time imagery of the entire Sun. This coupled with the high cadence, broad thermal coverage, and the large dynamic range of the Atmospheric Imaging Assembly on SDO has allowed discovery of impulsive solar disturbances that can significantly affect a hemisphere or more of the solar volume. Such events are often, but not always, associated with M and X class flares. GOES C and even B class flares are also associated with these large scale disturbances. Key to the recognition of the large scale disturbances was the creation of log difference movies. By taking the log of images before differencing events in the corona become much more evident. Because such events cover such a large portion of the solar volume their passage can effect the dynamics of the entire corona as it adjusts to and recovers from their passage. In some cases this may lead to a another flare or filament ejection, but in general direct causal evidence of 'sympathetic' behavior is lacking. However, evidence is accumulating these large scale events create an environment that encourages other solar instabilities to occur. Understanding the source of these events and how the energy that drives them is built up, stored, and suddenly released is critical to understanding the origins of space weather. Example events and comments of their relevance will be presented.

  7. A study of geomagnetic field variations along the 80° S geomagnetic parallel

    NASA Astrophysics Data System (ADS)

    Lepidi, Stefania; Cafarella, Lili; Francia, Patrizia; Piancatelli, Andrea; Pietrolungo, Manuela; Santarelli, Lucia; Urbini, Stefano

    2017-01-01

    The availability of measurements of the geomagnetic field variations in Antarctica at three sites along the 80° S geomagnetic parallel, separated by approximately 1 h in magnetic local time, allows us to study the longitudinal dependence of the observed variations. In particular, using 1 min data from Mario Zucchelli Station, Scott Base and Talos Dome, a temporary installation during 2007-2008 Antarctic campaign, we investigated the diurnal variation and the low-frequency fluctuations (approximately in the Pc5 range, ˜ 1-7 mHz). We found that the daily variation is clearly ordered by local time, suggesting a predominant effect of the polar extension of midlatitude ionospheric currents. On the other hand, the pulsation power is dependent on magnetic local time maximizing around magnetic local noon, when the stations are closer to the polar cusp, while the highest coherence between pairs of stations is observed in the magnetic local nighttime sector. The wave propagation direction observed during selected events, one around local magnetic noon and the other around local magnetic midnight, is consistent with a solar-wind-driven source in the daytime and with substorm-associated processes in the nighttime.

  8. High Amplitude Events in relation to Interplanetary disturbances

    NASA Astrophysics Data System (ADS)

    Mishra, Rajesh Kumar; Agarwal Mishra, Rekha

    2012-07-01

    The Sun emits the variable solar wind which interacts with the very local interstellar medium to form the heliosphere. Hence variations in solar activity strongly influence interplanetary space, from the Sun's surface out to the edge of the heliosphere. Superimposed on the solar wind are mass ejections from the Sun and/or its corona which, disturb the interplanetary medium - hence the name "interplanetary disturbances". Interplanetary disturbances are the sources of large-scale particle acceleration, of disturbances in the Earth's magnetosphere, of modulations of galactic cosmic rays in short, they are the prime focus for space weather studies. The investigation deals with the study of cosmic ray intensity, solar wind plasma and interplanetary magnetic field parameters variation due to interplanetary disturbances (magnetic clouds) during an unusual class of days i.e. high amplitude anisotropic wave train events. The high amplitude anisotropic wave train events in cosmic ray intensity has been identified using the data of ground based Goose Bay neutron monitor and studied during the period 1981-94. Even though, the occurrence of high amplitude anisotropic wave trains does not depend on the onset of interplanetary magnetic clouds. But the possibility of occurrence of these events cannot be overlooked during the periods of interplanetary magnetic cloud events. It is observed that solar wind velocity remains higher (> 300) than normal and interplanetary magnetic field B remains lower than normal on the onset of interplanetary magnetic cloud during the passage of these events. It is also noted from the superposed epoch analysis of cosmic ray intensity and geomagnetic activity for high amplitude anisotropic wave train events during the onset of interplanetary magnetic clouds that the increase in cosmic ray intensity and decrease in geomagnetic activity start not at the onset of magnetic clouds but after few days. The north south component of IMF (Bz), IMF (B), proton

  9. 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)

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

    2014-06-01

    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.

  10. The magnetospheric disturbance ring current as a source for probing the deep earth electrical conductivity

    USGS Publications Warehouse

    Campbell, W.H.

    1990-01-01

    Two current rings have been observed in the equatorial plane of the earth at times of high geomagnetic activity. An eastward current exists between about 2 and 3.5 earth radii (Re) distant, and a larger, more variable companion current exists between about 4 and 9 Re. These current regions are loaded during geomagnetic substorms. They decay, almost exponentially, after the cessation of the particle influx that attends the solar wind disturbance. This review focuses upon characteristics needed for intelligent use of the ring current as a source for induction probing of the earth's mantle. Considerable difficulties are found with the assumption that Dst is a ring-current index. ?? 1990 Birkha??user Verlag.

  11. Improving geomagnetic observatory data in the South Atlantic Anomaly

    NASA Astrophysics Data System (ADS)

    Matzka, Jürgen; Morschhauser, Achim; Brando Soares, Gabriel; Pinheiro, Katia

    2016-04-01

    The Swarm mission clearly proofs the benefit of coordinated geomagnetic measurements from a well-tailored constellation in order to recover as good as possible the contributions of the various geomagnetic field sources. A similar truth applies to geomagnetic observatories. Their scientific value can be maximised by properly arranging the position of individual observatories with respect to the geometry of the external current systems in the ionosphere and magnetosphere, with respect to regions of particular interest for secular variation, and with respect to regions of anomalous electric conductivity in the ground. Here, we report on our plans and recent efforts to upgrade geomagnetic observatories and to recover unpublished data from geomagnetic observatories at low latitudes in the South Atlantic Anomaly. In particular, we target the magnetic equator with the equatorial electrojet and low latitudes to characterise the Sq- and ring current. The observatory network that we present allows also to study the longitudinal structure of these external current systems. The South Atlantic Anomaly region is very interesting due to its secular variation. We will show newly recovered data and comparisons with existing data sets. On the technical side, we introduce low-power data loggers. In addition, we use mobile phone data transfer, which is rapidly evolving in the region and allows timely data access and quality control at remote sites that previously were not connected to the internet.

  12. Plasma drifts and polarization electric fields associated with TID-like disturbances in the low-latitude ionosphere: C/NOFS observations

    NASA Astrophysics Data System (ADS)

    Huang, Chao-Song

    2016-02-01

    Medium-scale traveling ionospheric disturbances are often observed at the magnetically conjugate points in the nighttime midlatitude ionosphere. It has been suggested that gravity waves disturb the ionosphere and induce electric fields in one hemisphere and that the electric fields are amplified by the Perkins instability and transmitted along the geomagnetic field lines to the conjugate ionosphere, creating similar disturbances there. However, direct observations of electric fields associated with traveling ionospheric disturbances (TIDs) are very few. In this study, we present low-latitude TID-like disturbances observed by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. It is found that ion velocity perturbations are generated in the directions parallel and perpendicular to the geomagnetic field within TIDs. Both the parallel and perpendicular ion velocity perturbations show an in-phase correlation with the ion density perturbations. For nighttime TIDs, the amplitude of both the parallel and meridional ion velocity perturbations increases almost linearly with the amplitude of the ion density perturbations, and the meridional ion drift is proportional to the parallel ion velocity. For daytime TIDs, the parallel ion velocity perturbation increases with the ion density perturbation, but the meridional ion velocity perturbation does not change much. The observations provide evidence that polarization electric field is generated within TIDs at low latitudes and maps along the geomagnetic field lines over a large distance.

  13. Using IRI and GSM TIP model results as environment for HF radio wave propagation model during the geomagnetic storm occurred on September 26-29, 2011

    NASA Astrophysics Data System (ADS)

    Kotova, D. S.; Klimenko, M. V.; Klimenko, V. V.; Zakharov, V. E.; Ratovsky, K. G.; Nosikov, I. A.; Zhao, B.

    2015-11-01

    This paper analyses the geomagnetic storm on September 26-29, 2011. We compare the calculation results obtained using the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) and IRI-2012 (Bilitza et al., 2014) model with ground-based ionosonde data of stations at different latitudes and longitudes. We examined physical mechanisms responsible for the formation of ionospheric effects during the main phase of geomagnetic storm that occurred at the rising phase of the 24th solar cycle. We used numerical results obtained from IRI-2012 and GSM TIP models as propagation environment for HF signals from an equatorial transmitter during quiet and disturbed conditions. We used the model of HF radio wave propagation developed in I. Kant Baltic Federal University (BFU) that is based on the geometrical optics approximation. We compared the obtained radio paths in quiet conditions and during the main and recovery storm phases and evaluated radio wave attenuation in different media models.

  14. The variations of geomagnetic field in the region of the Sulaksky cascade of hydro-electric power station

    NASA Astrophysics Data System (ADS)

    Daniyalov, M. G.; Suleymanov, A. I.

    2012-04-01

    Technogenic intervention in nature while creation of large water basins disturbs developed dynamic balance in rock mass and activates seismic processes, i.e. causes the so-called exited earthquakes which are connected with water basin operation. Local changes of a magnetic field of the Earth can be the result of various physical processes, but the most probable - electromagnetic and piezomagnetic processes. In our case the rock piezomagnetism is considered to be the principal cause of local geomagnetic variations - change of their magnetization under the influence of mechanical pressure. The measurements were made 2 times a day at the same time to reveal the connection of geomagnetic field components variations with water basin level fluctuations. According to geomagnetic measurements of 1983-1989 it is determined, that relative changes of a vertical component δΖ much more exceed respective alterations of the module of a full vector δT that is indirect acknowledgement of magnetoelastic effect under natural conditions. We determined that in the period of intensive rising of water level and weight the sharp reduction of a vertical component in water basin is observed which depends not only on loading value, but also on filling speed. At stable level of a water basin slight increase of δΖ is observed which is explained by internal pressure relaxation process in the water basin basis. The empirical formula for calculation of changes of a vertical component of a field ΔΖ under the influence of loading during the water basin filling is observed. The numerical value of coefficient k,, calculated by the least square method as the interconnection coefficient between vertical component changes and changes of level of the Chirkeysky water basin according to measurements of 1983-1989 is: 5, 66 10-4 nano-tesla / Pa. Ju. Skovorodkin obtained the numerical value of k coefficient: 6, 3 10-6 nano-tesla / Pa during the variations measurements of full vector module of

  15. Coronal disturbances and their terrestrial effects /Tutorial Lecture/

    NASA Technical Reports Server (NTRS)

    Rust, D. M.

    1983-01-01

    An assessment is undertaken of recent approaches to the prediction of the interplanetary consequences of coronal disturbances, with attention to the relationships of shocks and energetic particles to coronal transients, of proton events to gamma-ray and microwave bursts, of geomagnetic storms to filament eruptions, and of solar wind increases to the flare site magnetic field direction. A discussion is given concerning the novel phenomenon of transient coronal holes, which appear astride the long decay enhancements of 2-50 A X-ray emission following H-alpha filament eruptions. These voids in the corona are similar to long-lived coronal holes, which are the sources of high speed solar wind streams. The transient coronal holes may also be associated with transient solar wind speed increases.

  16. Determination of geomagnetic archaeomagnitudes from clay pipes

    NASA Astrophysics Data System (ADS)

    Games, K. P.; Baker, M. E.

    1981-02-01

    Archaeomagnitude determinations of a selection of clay pipes dateable to AD 1645+/-10 as well as studies of pottery samples from the same site and of the same age have been made. Values of the magnitude of the ancient magnetic field (Banc), were obtained from two pottery sherds, two pipe bowls and three pipe stems. The values from the sherds and bowls agree within 2% and compare well with the average value of the magnitude of the magnetic field for the seventeenth century as determined by other archaeomagnetic studies. However, the pipe stems give values of Banc which are significantly less than those from the bowls and pottery. We have not yet been able to explain this and thus we suggest that reliable archaeomagnitude determinations can be made from the bowls of clay pipes but not from the stems. Nevertheless, this result provides a new source of material for investigating variations in the geomagnetic field strength over the past 400 yr. Clay pipes have been manufactured in England since the end of the sixteenth century. In the firing process some pipes were broken and disposed of without ever having been smoked. One such collection, discovered at Rainford, Lancashire, in 1978, consisted of a series of discrete dumps including pipes, kiln debris and a small collection of contemporary used earthenware sherds. The internal consideration of the dumps suggested a very short period of activity and archaeologists (P. Davey, personal communication) ascribe all the material to the period 1645+/-10 yr. With such well-dated material, we set out to check whether or not reliable archaeomagnitudes could be obtained from the pipes.

  17. Airport geomagnetic surveys in the United States

    USGS Publications Warehouse

    Berarducci, A.

    2006-01-01

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

  18. Satellite accelerometer measurements of neutral density and winds during geomagnetic storms

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    A new thermospheric wind measurement technique is reported which is based on a Satellite Electrostatic Triaxial Accelerometer (SETA) system capable of accurately measuring accelerations in the satellite's in-track, cross-track and radial directions. Data obtained during two time periods are presented. The first data set describes cross-track winds measured between 170 and 210 km during a 5-day period (25 to 29 March 1979) of mostly high geomagnetic activity. In the second data set, cross-track winds and neutral densities from SETA and exospheric temperatures from the Millstone Hill incoherent scatter radar are examined during an isolated magnetic substorm occurring on 21 March 1979. A polar thermospheric wind circulation consisting of a two cell horizontal convection pattern is reflected in both sets of cross-track acceleration measurements. The density response is highly asymmetric with respect to its day/night behavior. Latitude structures of the density response at successive times following the substorm peak suggest the equatorward propagation of a disturbance with a phase speed between 300 and 600 m/s. A deep depression in the density at high latitudes (less than 70 deg) is evident in conjunction with this phenomenon. The more efficient propagation of the disturbance to lower latitudes during the night is probably due to the midnight surge effect.

  19. Multi-station observation of ionospheric irregularities over South Africa during strong geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Amabayo, Emirant Bertillas; Cilliers Pierre, J.

    2013-03-01

    This paper presents results pertaining to the response of the mid-latitude ionosphere to strong geomagnetic storms that occurred from 31 March to 02 April 2001 and 07-09 September 2002. The results are based on (i) Global Positioning Systems (GPSs) derived total electron content (TEC) variations accompanying the storm, (ii) ionosonde measurements of the ionospheric electrodynamic response towards the storms and (iii) effect of storm induced travelling ionospheric disturbances (TIDs) on GPS derived TEC. Ionospheric data comprising of ionospheric TEC obtained from GPS measurements, ionograms, solar wind data obtained from Advanced Composition Explorer (ACE) and magnetic data from ground based magnetometers were used in this study. Storm induced features in vertical TEC (VTEC) have been obtained and compared with the mean VTEC of quiet days. The response of the mid-latitude ionosphere during the two storm periods examined may be characterised in terms of increased or decreased level of VTEC, wave-like structures in VTEC perturbation and sudden enhancement in hmF2 and h‧F. The study reveals both positive and negative ionospheric storm effects on the ionosphere over South Africa during the two strong storm conditions. These ionospheric features have been mainly attributed to the travelling ionospheric disturbances (TIDs) as the driving mechanism for the irregularities causing the perturbations observed. TEC perturbations due to the irregularities encountered by the satellites were observed on satellites with pseudo random numbers (PRNs) 15, 17, 18 and 23 between 17:00 and 23:00 UT on 07 September 2002.

  20. Geomagnetic and solar activity dependence of ionospheric upflowing O+: FAST observations

    NASA Astrophysics Data System (ADS)

    Zhao, K.; Jiang, Y.; Chen, K. W.; Huang, L. F.

    2016-09-01

    This paper investigates the dependence of the occurrence frequency of ionospheric upflowing oxygen (O+) ions on the sunspot cycle and geomagnetic activity. We examine the upflows response to the geomagnetic disturbances as well as the influence of the ion energy factor in controlling the magnitude of the occurrence frequency and the net energy flux. We discuss the spatial distribution of the upflow occurrence frequency and construct a regression model as a function of the magnetic latitude. The results show an overall enhancement of the upflow occurrence frequency during magnetically disturbed periods and indicate that the high-occurrence area spreads out from the source regions during magnetically quiet periods. The high-occurrence areas are located at 70° magnetic latitude (mLat) in the dayside auroral oval zone and between 76-80° mLat in the dayside polar cusp region. In the nightside auroral oval zone, these areas are near 60° mLat, penetrating further equatorward to 55° mLat during magnetically disturbed periods. High energy (≥1 keV) upflowing ions are common in the nightside auroral oval zone while low energy (<1 keV) upflowing ions are found escaping from the high latitude dayside cusp region. A Gaussian function is shown to be a good fit to the occurrence frequency over the magnetic latitude. For high energy upflowing O+ ions, the occurrence frequency exhibits a single peak located at about 60° mLat in the nightside auroral oval zone while for low energy upflowing O+ ions, it exhibits two peaks, one near 60° mLat in the auroral oval zone and the other near 78° mLat in the cusp region. We study the solar activity dependence by analyzing the relationship between the upflow occurrence frequency and the sunspot number (RZ). The statistical result shows that the frequency decreases with declining solar activity level, from ˜30 % at solar maximum to ˜5 % at solar minimum. In addition, the correlation coefficient between the occurrence frequency and RZ

  1. Vehicle Disturbance Test

    NASA Astrophysics Data System (ADS)

    Clapp, Brian

    2009-07-01

    The purpose of the VDT is to measure and characterize uncompensated environmental disturbances acting upon the HST during normal operation. The VDT is a passive test {not a forced-response test} used to obtain signatures for both externally induced {e.g. SCM, SA-3, SSM thermal gradients} and internally induced {e.g. HGA, RWA, COS and WFC3 mechanisms} disturbances affecting HST LOS pointing. The disturbances observed will be used as the nominal on-orbit disturbances in pointing control simulations until the next VDT is run.The test occurs after release, and most of the VDT can be run during the BEA period. The ?V1 sunpoint portion of the VDT usually occurs after the BEA period is complete. The VDT shall consist of two separate tests that need not occur consecutively. The overall duration of the VDT is at least 13 orbits of spacecraft time including {1} at least 8 orbits at +V3 sunpoint after achieving thermal equilibrium {at least 36-hours at +V3 sunpoint} and three out of 8-orbits have RWA Friction Compensation turned Off, and {2} at least 5 orbits at ?V1 sunpoint {all or part of this segment have RWA Friction Compensation turned Off}. At the beginning of each test, the attitude control law gains are switched to maneuver gains, and the gyros are commanded to low mode. The nominal attitude control law configuration will be restored at the end of each test.Each test is initiated via SMS execution of stored program macros in the HST flight computer to switch the attitude control law gains to low-bandwidth maneuver gains, command the gyros into low mode, terminate Velocity aberration and parallax {VAP} processing, and manage the status of on-board RWA Friction Compensation. The nominal attitude control law configuration will be restored at the end of each test via SMS execution of stored program macros. The stored program command macros are developed specifically for the VDT by the Flight Software and Pointing Control System groups.

  2. Sleep Disturbances in Neurodevelopmental Disorders.

    PubMed

    Robinson-Shelton, Althea; Malow, Beth A

    2016-01-01

    Sleep disturbances are extremely prevalent in children with neurodevelopmental disorders compared to typically developing children. The diagnostic criteria for many neurodevelopmental disorders include sleep disturbances. Sleep disturbance in this population is often multifactorial and caused by the interplay of genetic, neurobiological and environmental overlap. These disturbances often present either as insomnia or hypersomnia. Different sleep disorders present with these complaints and based on the clinical history and findings from diagnostic tests, an appropriate diagnosis can be made. This review aims to provide an overview of causes, diagnosis, and treatment of sleep disturbances in neurodevelopmental disorders that present primarily with symptoms of hypersomnia and/or insomnia.

  3. Magnetospheric mapping with a quantitative geomagnetic field model

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Mapping the magnetosphere on a dipole geomagnetic field model by projecting field and particle observations onto the model is described. High-latitude field lines are traced between the earth's surface and their intersection with either the equatorial plane or a cross section of the geomagnetic tail, and data from low-altitude orbiting satellites are projected along field lines to the outer magnetosphere. This procedure is analyzed, and the resultant mappings are illustrated. Extension of field lines into the geomagnetic tail and low-altitude determination of the polar cap and cusp are presented. It is noted that while there is good agreement among the various data, more particle measurements are necessary to clear up statistical uncertainties and to facilitate comparison of statistical models.

  4. Midlatitude cooling caused by geomagnetic field minimum during polarity reversal.

    PubMed

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

    2013-01-22

    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.

  5. The geomagnetic elements in Denmark 1928-1980

    NASA Astrophysics Data System (ADS)

    Hansen, H. A.

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

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

    USGS Publications Warehouse

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1983-09-01

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

  8. Report of geomagnetic pulsation indices for space weather applications

    USGS Publications Warehouse

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

    2013-01-01

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

  9. Regional Geomagnetic Field Model for Croatia at 2009.5

    NASA Astrophysics Data System (ADS)

    Vujić, Eugen; Brkić, Mario; Kovács, Peter

    2016-02-01

    Geomagnetic data of north, east, and vertical components at Croatian repeat stations and ground survey sites, as well as European geomagnetic observatories and repeat stations, were used to obtain a regional geomagnetic model over Croatia at 2009.5 epoch. Different models were derived, depending on input data, and three modelling techniques were used: Taylor Polynomial, Adjusted Spherical Harmonic Analysis, and Spherical Harmonic Analysis. It was derived that the most accurate model over Croatia was the one when only Croatian data were used, and by using the Adjusted Spherical Harmonic Analysis. Based on Croatian repeat stations' data in the interval 2007.5-2010.5, and a global Enhanced Magnetic Model, it was possible to estimate the crustal field at those sites. It was also done by taking into account the empirical adjustment for long-term external field variations. The higher crustal field values were found at those stations which are on or close to the Adriatic anomaly.

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

    NASA Astrophysics Data System (ADS)

    Aubert, Julien; Fournier, Alexandre

    2013-04-01

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

  11. Electric currents above Saint-Santin 3. A preliminary study of disturbances: June 6, 1978; March 22, 1979; March 23, 1979

    SciTech Connect

    Mazaudier, C.

    1985-02-01

    This paper presents three case studies of ionospheric disturbances in electric fields, currents, and winds during periods of geomagnetic storms. These disturbances are detected by the Saint-Santin incoherent scatter radar. The disturbances are shown to originate from two distinct physical mechanism: (1) penetration of electric fields to lower latitudes during times of rapid change in magnetospheric convection; and (2) the action of the disturbed ionospheric dynamo driven by storm-induced wind disturbances. The storm of June 6, 1978, shows a simple illustration of penetrative convection electric fields. The storm of March 22, 1979, gives additional examples of this effect both when the B/sub Z/ component of the interplanetary fields turns southward and northward. The observed events on March 23 are clearly identifiable as the delayed response of the disturbance ionospheric dynamo.

  12. Geomagnetic Storm Main Phase effect on the Equatorial Ionosphere as measured from GPS observations at Ile-Ife

    NASA Astrophysics Data System (ADS)

    Olabode, Ayomide; Ariyibi, Emmanuel

    2016-07-01

    The effect of the main phase of two intense geomagnetic storm events which occurred on August 5-6 and September 26-27, 2011 on the equatorial ionosphere have been investigated using Global Positioning System (GPS) data obtained from an Ile-Ife station (geomagnetic lat. 9.84°N, long. 77.25°E). The WinTEC-P and GPS-TEC analysis software programs were used to process the GPS data to obtain Total Electron Content (TEC) and Scintillation Index (S4). TEC profiles during the main phase of the two geomagnetically disturbed days were compared with quiet time average profiles to examine the response of the equatorial ionosphere. International Reference Ionosphere (IRI) 2012 TEC model was also obtained from Virtual Ionosphere, Thermosphere, Mesosphere Observatory (VITMO) and the extents of deviation from measured GPS-derived TEC were examined for the main phase of the storm events. The results showed that the intensity of both storm events during the main phase which occurred at night-time correlated well with a strong southward direction of the z-component of the Interplanetary Magnetic Field (IMF-Bz) and Solar Wind Speed (Vsw), with the Disturbance storm time (Dst) profile showing multiple step development. TEC depletion was observed during the main phase of the August 5-6, 2011 storm event with TEC recording a maximum value of 9.31 TECU. A maximum TEC value of 55.8 TECU was recorded during the main phase of the September 26-27, 2011 storm event depicting TEC enhancement. Significant scintillation index value of 0.57 was observed when the main phase started on August 5-6, 2011 followed by a prolonged suppression while there was less significant scintillation impact on September 26-27, 2011 with a maximum value of 0.33. The study concluded that the intensification of the ring current during the main phase of geomagnetic storm events was responsible for the intensity of the storm events causing large variations in TEC and significant scintillation phenomenon.

  13. Soil disturbance by airbags

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Disturbance of the drift at the Pathfinder landing site reveals a shallow subsurface that is slightly darker but has similar spectral properties. The top set of images, in true color, shows the soils disturbed by the last bounce of the lander on its airbags before coming to rest and the marks created by retraction of the airbags. In the bottom set of images color differences have been enhanced. The mast at center is the Atmospheric Structure Instrument/Meteorology Package (ASI/MET). The ASI/MET is an engineering subsytem that acquired atmospheric data during Pathfinder's descent, and will continue to get more data through the entire landed mission. A shadow of the ASI/MET appears on a rock at left.

    Mars Pathfinder was developed and managed by the Jet Propulsion Laboratory (JPL) for the National Aeronautics and Space Administration. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  14. GEOMAGNETIC REVERSALS DRIVEN BY ABRUPT SEA LEVEL CHANGES

    SciTech Connect

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

    1986-10-01

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

  15. Effects of a geomagnetic storm on thermospheric circulation. Master's thesis

    SciTech Connect

    Brinkman, D.G.

    1987-01-01

    The motions of the thermosphere and its interactions with the ionosphere during a geomagnetic storm are of current interest to space scientists. A two-dimensional model was used to simulate the thermospheric response to the impulsive high-latitude heating associated with a geomagnetic storm. The storm-induced motions can be characterized by an initial period of transient waves followed by the development of a mean circulation. These motions generate an electrical-current system that is on the same order of magnitude as, and in the opposite sense to the normal s/sub q/ current system. Model-simulated winds and electrical currents were then compared to observations.

  16. Poloidal and toroidal fields in geomagnetic field modeling

    NASA Astrophysics Data System (ADS)

    Backus, G.

    1986-02-01

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

  17. Secular Variations of the Geomagnetic Field in Europe

    NASA Astrophysics Data System (ADS)

    Sas-Uhrynowski, A.; Welker, E.

    2009-09-01

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

  18. Equatorial Ionospheric Irregularities Observed in the South American Sector During the December 2006 Geomagnetic Storm

    NASA Astrophysics Data System (ADS)

    Sahai, Y.; de Jesus, R.; Guarnieri, F. L.; Fagundes, P. R.; de Abreu, A. J.; Becker-Guedes, F.; Abalde, J. R.; Brunini, C.; Gende, M.; Cintra, T.; de Souza, V.; Pillat, V.; Lima, W.

    2009-05-01

    This investigation presents studies related to the observations of equatorial ionospheric irregularities in the ionospheric F-region in the South American sector during the intense geomagnetic storm in December 2006, during the period of low solar activity. The geomagnetic storm reached a minimum Dst of -147 nT at 0700 UT on 15 December. In this work ionospheric sounding data obtained between 13 and 16 December 2006 at Palmas (PAL; 10.2o S, 48.2o W; dip latitude 6.6o S) and São José dos Campos (SJC, 23.2o S, 45.9o W; dip latitude 17.6o S), Brazil, and Jicamarca (JIC, 12.0o S, 76.8o W; dip latitude 0.05o S), Peru, have been used. Also, vertical total electron content (VTEC) and phase fluctuations (TECU/min) from GPS observations obtained at Brasilia (BRAZ, 15.9o S, 47.9o W; dip latitude 11.7o S), Presidente Prudente (PPTE, 22.12° S, 51.4° W; dip latitude 14,9° S), Curitiba (PARA, 25.43o S, 49.21o W; dip latitude 18.4o S), Santa Maria (SMAR, 29.71o S, 53.07o W; dip latitude 19.6o S), Brazil, Bahia Blanca (VBCA, 38.7o S, 62.3o W; dip latitude 22.4o S) and Puerto Deseado (PDES, 47.7o S, 65.9o W, dip latitude 27.1o S), Argentina, during the period 13 to 16 December are presented. An unusual uplifting of the F-region during pre-reversal enhancement (PRE) on 14 December was possibly associated with a prompt penetration of electric field of magnetospheric origin after the storm sudden commencement (1414 UT on 14 December). On this geomagnetically disturbed night of 14-15 December, intense equatorial ionospheric irregularities were observed up to southern most GPS station PDES in Argentina. It should be mentioned that on the other nights viz., 12-13 and 13-14 December (both nights before the storm), and 15-16 December (recovery phase), the ionospheric irregularities are limited to only the Brazilian GPS stations. On the geomagnetically disturbed night of 14-15 December, strong oscillations were observed in the F-region base height possibly associated with Joule heating

  19. Anomalous night-time peaks in diurnal variations of NmF2 close to the geomagnetic equator: a statistical study

    NASA Astrophysics Data System (ADS)

    Pavlov, Anatoli

    We present a study of anomalous night-time NmF2 peaks, ANNPs, observed by the La Paz, Natal, Djibouti, Kodaikanal, Madras, Manila, Talara, and Huancayo-Jicamarca ionosonde stations close to the geomagnetic equator. It is shown that the probabilities of occurrence of the first and second ANNPs depend on the geomagnetic longitude, and there is a longitude sector close to 110° geomagnetic longitude where the first and second ANNPs occur less frequently in comparisons with the longitude regions located close to and below about 34° geomagnetic longitude and close to and above about 144° geomagnetic longitude. The found frequencies of occurrence of the ANNPs increase with increasing solar activity, except of the Djibouti and Kodaikanal ionosonde stations, where the probability of the first ANNP occurrence is found to decrease with increasing solar activity from low (F10.7<100) to moderate (100≤F10.7≤170) solar activity, and except of the Natal ionosonde station, where the frequencies of occurrence of the first and second ANNPs decrease with increasing solar activity from moderate to high (F10.7>170) solar activity. We found that the occurrence probabilities of ANNPs during geomagnetically disturbed conditions are greater than those during geomagnetically quiet conditions. The calculated values of these probabilities have pronounced maximums in June (La-Paz and Talara) and in July (Huancayo-Jicamarca) at the ionosonde stations located in the southern geographic hemisphere. The first ANNP is least frequently observed in January (La-Paz, Talara, and Huancayo-Jicamarca), and the second ANNP is least frequently measured in January (La-Paz and Huancayo-Jicamarca) and in December (Talara). In the northern geographic hemisphere, the studied probabilities are lowest in June (Djibouti and Madras), in July (Manila), and in April (Kodaikanal). The maximums in the probabilities of occurrence of the first and second ANNPs are found to be in September (Djibouti), in October

  20. Effects of solar and geomagnetic activity on the occurrence of equatorial plasma bubbles over Hong Kong

    NASA Astrophysics Data System (ADS)

    Kumar, Sanjay; Chen, Wu; Liu, Zhizhao; Ji, Shengyue

    2016-09-01

    In the present study, the occurrence and characteristics of equatorial plasma bubble (EPB) has been analyzed using the GPS data from continuously operating reference stations network over Hong Kong during 2001-2012. The analysis found maximum EPB occurrences during the equinoctial months and minimum EPB occurrences during the December solstice throughout 2001-2012 except during the solar minimum in 2007-2009. The maximum EPB occurrences were observed in June solstice during 2007-2008, whereas for 2009, EPB occurrences were quite higher for June solstice but slightly smaller than the March equinox. The seasonal maximum in EPB occurrences have been discussed in terms of plasma density seed perturbation caused by gravity waves as well as the post sunset F-layer rise due to the pre-reversal enhancement of zonal electric field. Generally, EPB occurrences are found to be more prominent during nighttime hours (19:00-24:00 h) than daytime hours. The day and nighttime EPB occurrences were inferred and found to vary linearly with solar activity and have an annual correlation coefficient (R) of 0.92 with F10.7 cm solar flux and 0.88 with sunspot number. Moreover, the impact of solar activity on EPB occurrences is found to be dependent on seasons with maximum during the equinox (R = 0.80) and minimum during the summer season (R = 0.68). The detail study of EPB occurrences during two typical cases of geomagnetic storms on 6 November and 24 November 2001 found that the storm on 24 November triggered the EPB occurrence whereas storm on 6 November suppressed the EPB occurrence. The enhancement/suppression of EPB occurrences during storms periods is a consequence of a storm-induced prompt penetration electric field as well as disturbance dynamo electric field effects associated with the main phase of the geomagnetic storm.

  1. Quantitative maps of geomagnetic perturbation vectors during substorm onset and recovery

    PubMed Central

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

    2015-01-01

    We have produced the first series of spherical harmonic, numerical maps of the time-dependent surface perturbations in the Earth's magnetic field following the onset of substorms. Data from 124 ground magnetometer stations in the Northern Hemisphere at geomagnetic latitudes above 33° were used. Ground station data averaged over 5 min intervals covering 8 years (1998–2005) were used to construct pseudo auroral upper, auroral lower, and auroral electrojet (AU*, AL*, and AE*) indices. These indices were used to generate a list of substorms that extended from 1998 to 2005, through a combination of automated processing and visual checks. Events were sorted by interplanetary magnetic field (IMF) orientation (at the Advanced Composition Explorer (ACE) satellite), dipole tilt angle, and substorm magnitude. Within each category, the events were aligned on substorm onset. A spherical cap harmonic analysis was used to obtain a least error fit of the substorm disturbance patterns at 5 min intervals up to 90 min after onset. The fits obtained at onset time were subtracted from all subsequent fits, for each group of substorm events. Maps of the three vector components of the averaged magnetic perturbations were constructed to show the effects of substorm currents. These maps are produced for several specific ranges of values for the peak |AL*| index, IMF orientation, and dipole tilt angle. We demonstrate an influence of the dipole tilt angle on the response to substorms. Our results indicate that there are downward currents poleward and upward currents just equatorward of the peak in the substorms' westward electrojet. Key Points Show quantitative maps of ground geomagnetic perturbations due to substorms Three vector components mapped as function of time during onset and recovery Compare/contrast results for different tilt angle and sign of IMF Y-component PMID:26167445

  2. Comparison of Ionospheric TEC Derived from GPS and IRI 2012 Model during Geomagnetic Storms at Indonesia

    NASA Astrophysics Data System (ADS)

    Marlia, Dessi; Wu, Falin

    2016-07-01

    This paper investigates the variations of vertical Total Electron Content (VTEC) at Manado, Indonesia (geographic coordinates : lat 1.34 ° S and long 124.82 ° E) for period 2013. The GPS measured TEC is compared with the TEC derived from the IRI (International Reference Ionosphere) 2012 model. Vertical TEC measurements obtained from dual frequency GPS receiver that is GISTM (GPS Ionospheric Scintillations and TEC monitor). Variation of TEC validate to IRI 2012 model at Manado station has been compared with the model for three different topside of electron density namely NeQuick, IRI-01-Corr and IRI2001.There is a need to investigation on diurnal, seasonal variations, solar activity dependence of TEC and including effects of space weather related events to TEC and modeling of TEC. In this paper, diurnal and seasonal variations of VTEC and the effect of VTEC due to space weather events like Geomagnetic storms are analyzed. The result show that the TEC prediction using IRI-2001 model overestimated the GPS TEC measurements, while IRI-NeQuick and IRI-01-corr show a tendency to underestimates the observed TEC during the day time particularly in low latitude region in the maximum solar activity period (2013). The variations of VTEC during 17th March, 2013, 29th June, 2013 storms are analyzed. During 17th March,2013 storm enhancement in VTEC with Kp value 6 and Disturbance storm index (DST) -132 nT. During 29th June, 2013 storm VTEC depletion with value 7 and DST -98 nT. Significant deviations in VTEC during the main phase of the storms are observed. It is found that the response of ionospheric TEC consist of effects of both enhancement and depletions in ionospheric structures (positive and negative storm). Keywords: TEC ionosphere, GPS, GISTM, IRI 2012 model, solar activity, geomagnetic storm

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  4. Prediction of Geomagnetic Storm Strength from Inner Heliospheric In Situ Observations

    NASA Astrophysics Data System (ADS)

    Kubicka, M.; Moestl, C.; Rollett, T.; Feng, L.; Eastwood, J. P.; Boakes, P. D.

    2015-12-01

    In order to predict the effects of interplanetary coronal mass ejections (ICMEs) on Earth, it is important to know the properties of the interplanetary magnetic field (IMF). Of special interest is the southward component (Bz) of the IMF, acting as a main driver for geomagnetic storms. We are working on a proof-of-concept for predicting the strength of geomagnetic storms caused by ICMEs by using in situ data from spacecraft in the inner heliosphere. Our prediction includes the arrival time and speed of the ICME at Earth, the IMF's Bz component and the resulting disturbance storm time index (Dst), which is a prime indicator of geomagnetic activity. For Dst forecasting, the two well established models Burton et al. (1975) and O'Brien & McPherron (2000) are used. Necessary parameters for those models are the ICME speed and the Bz component of the IMF at 1 AU. We obtain the ICME speed using a drag-based model, and the IMF's Bz component is predicted based on a power law from the in situ data. Additionally, the ENLIL/WSA model provides the solar wind background speed for the drag-based model.An advantage of our method is the use of the in situ spacecraft as a reference point for the drag based-model, leading to a more precise arrival speed of the ICME at Earth, and an improved arrival time. Investigation of an ICME in June 2012 shows already very promising results for the Dst index, as well as for the ICME arrival speed. The main advantage of this method is the prediction lead time of ~21 hours compared to only ~40-60 minutes, using an L1 located spacecraft. Furthermore, the feasibility of this method can be studied with any in situ spacecraft temporarily located between the Sun and Earth, like Helios, Solar Orbiter or Solar Probe Plus, and also works for radial spacecraft alignments. The techniques we develop could be routinely applied to a mission that forms an artificial Lagrange point along the Sun-Earth line, e.g. for a Sunjammer or Heliostorm mission.

  5. Low-latitude total electron content enhancement at low geomagnetic activity observed over Japan

    NASA Astrophysics Data System (ADS)

    Kutiev, Ivan; Otsuka, Yuichi; Saito, Akinori; Tsugawa, Takuya

    2007-07-01

    Numerous total electron content (TEC) values derived from GPS signals are averaged within 1.5° × 1.5° cells in a 1-hour time frame, and the relative deviations of these average values from corresponding monthly medians are used to produce latitude-time plots over Japan. The paper analyzes the appearance and development of enhancements of TEC of equatorial origin (ETEs), occurring outside initial and main phases of geomagnetic storms. ETE structures appear mainly as single-crest structures in the evening hours local time, with TEC peak around 1900 LT. TEC usually decreases with latitude, and the structures disappear below 40°N. In some cases the TEC peak is found above the plot boundary of 24°N, as depletions toward the equator are also observed. The observed enhanced structures are linked to the well-known evening prereversal enhancement of ion drift in the equatorial F region. Double-crest ETEs are also observed, with the second peak occurring in early morning hours. Most of the ETE events appear in periods of low geomagnetic activity, 1-3 days after the main phase of the storms. In some cases the time of rising of ETE structures coincides with the increase of interplanetary electric field (IEF), a fact showing the importance of directly penetrating electric field in formation of ETEs. Often, ETEs appear repeatedly in 2 or 3 consecutive days. It is supposed that planetary atmospheric waves are responsible for this phenomenon. Most of the observed features of ETEs can be explained by the published results of simulations of the coupled thermosphere-ionosphere-plasmasphere (CTIP) model and the thermosphere/ionosphere/electrodynamic general circulation model (TIEGCM). It is suggested that ETE structures are produced mainly by a disturbance winds dynamo electric field, built up after the main phase of the storms. Some ETE events, appearing at the end of a prolonged period of low geomagnetic activity, can be linked to directly penetrating IEF in equatorial

  6. Reaction Wheel Disturbance Reduction Method Using Disturbance Measurement Table

    NASA Astrophysics Data System (ADS)

    Cheon, Dong-Ik; Jang, Eun-Jeong; Oh, Hwa-Suk

    2011-12-01

    Momentum changing actuators like reaction wheels and control moment gyros are generally used for spacecraft attitude control. This type of actuators produces force and torque disturbances. These disturbances must be reduced since they degrade the quality of spacecraft attitude control. Major disturbances are mainly due to static and dynamic imbalances. This paper gives attention to the reduction of the static and dynamic imbalance. Force/torque measurement system is used to measure the disturbance of the test reaction wheel. An identification method for the location and magnitude of the imbalance is suggested, and the corrections of the imbalance are performed using balancing method. Through balancing, the static and dynamic imbalance is remarkably reduced

  7. A method for separating seismo-ionospheric TEC outliers from heliogeomagnetic disturbances by using nu-SVR

    SciTech Connect

    Pattisahusiwa, Asis; Liong, The Houw; Purqon, Acep

    2015-09-30

    Seismo-Ionospheric is a study of ionosphere disturbances associated with seismic activities. In many previous researches, heliogeomagnetic or strong earthquake activities can caused the disturbances in the ionosphere. However, it is difficult to separate these disturbances based on related sources. In this research, we proposed a method to separate these disturbances/outliers by using nu-SVR with the world-wide GPS data. TEC data related to the 26th December 2004 Sumatra and the 11th March 2011 Honshu earthquakes had been analyzed. After analyzed TEC data in several location around the earthquake epicenter and compared with geomagnetic data, the method shows a good result in the average to detect the source of these outliers. This method is promising to use in the future research.

  8. Empirical regional models for the short-term forecast of M3000F2 during not quiet geomagnetic conditions over Europe

    NASA Astrophysics Data System (ADS)

    Pietrella, M.

    2013-10-01

    improve significantly the predictions; (2) under disturbed geomagnetic conditions, the Bradley-Dudeney formula improves the predictions of RM_M3000F2 in the entire European area; (3) in the case of very disturbed geomagnetic conditions, the Bradley-Dudeney algorithm is very effective in improving the performance of IRI_RM_M3000F2; (4) under moderate geomagnetic conditions, the long-term prediction maps of M3000F2 generated by RM_M3000F2 can be considered as short-term forecasting maps providing very satisfactory results because quiet geomagnetic conditions are not so diverse from moderate geomagnetic conditions; (5) the forecasting maps originated by RM_M3000F2, RM_M3000F2_BD, and IRI_RM_M3000F2_BD show some regions where the forecasts are not satisfactory, but also wide sectors where the M3000F2 forecasts quite faithfully match the M3000F2 observations, and therefore RM_M3000F2, RM_M3000F2_BD, and IRI_RM_M3000F2_BD could be exploited to produce short-term forecasting maps of M3000F2 over Europe up to 3 h in advance.

  9. Long-lasting negative ionospheric storm effects in low and middle latitudes during the recovery phase of the 17 March 2013 geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Yue, Xinan; Wang, Wenbin; Lei, Jiuhou; Burns, Alan; Zhang, Yongliang; Wan, Weixing; Liu, Libo; Hu, Lianhuan; Zhao, Biqiang; Schreiner, William S.

    2016-09-01

    In this paper, an ionospheric electron density reanalysis algorithm was used to generate global optimized electron density during the 17-18 March 2013 geomagnetic storm by assimilating 10 low Earth orbit satellites based and 450 ground global navigation satellite system receiver-based total electron content into a background ionospheric model. The reanalyzed electron density could identify the large-scale ionospheric features quite well during storm time, including the storm-enhanced density, the positive ionospheric storm effect during the initial and main phases, and the negative ionospheric storm effect during the recovery phase. The simulations from the Thermosphere Ionosphere Electrodynamics General Circulation Model can reproduce similar large-scale ionospheric disturbances as seen in the reanalysis results. Both the reanalysis and simulations show long-lasting (>17 h) daytime negative storm effect over the Asia sector as well as hemispheric asymmetry during the recovery phase. Detailed analysis of the Global Ultraviolet Imager-derived O/N2 ratio and model simulations indicate that the polar ward meridional wind disturbance, the downward E × B drift disturbance and O/N2 depletion might be responsible for the negative storm effect. The hemispheric asymmetry is mainly caused by the geomagnetic field line configuration, which could cause hemispheric asymmetry in the O/N2 depletion.

  10. An empirical model of the quiet daily geomagnetic field variation

    USGS Publications Warehouse

    Yamazaki, Y.; Yumoto, K.; Cardinal, M.G.; Fraser, B.J.; Hattori, P.; Kakinami, Y.; Liu, J.Y.; Lynn, K.J.W.; Marshall, R.; McNamara, D.; Nagatsuma, T.; Nikiforov, V.M.; Otadoy, R.E.; Ruhimat, M.; Shevtsov, B.M.; Shiokawa, K.; Abe, S.; Uozumi, T.; Yoshikawa, A.

    2011-01-01

    An empirical model of the quiet daily geomagnetic field variation has been constructed based on geomagnetic data obtained from 21 stations along the 210 Magnetic Meridian of the Circum-pan Pacific Magnetometer Network (CPMN) from 1996 to 2007. Using the least squares fitting method for geomagnetically quiet days (Kp ??? 2+), the quiet daily geomagnetic field variation at each station was described as a function of solar activity SA, day of year DOY, lunar age LA, and local time LT. After interpolation in latitude, the model can describe solar-activity dependence and seasonal dependence of solar quiet daily variations (S) and lunar quiet daily variations (L). We performed a spherical harmonic analysis (SHA) on these S and L variations to examine average characteristics of the equivalent external current systems. We found three particularly noteworthy results. First, the total current intensity of the S current system is largely controlled by solar activity while its focus position is not significantly affected by solar activity. Second, we found that seasonal variations of the S current intensity exhibit north-south asymmetry; the current intensity of the northern vortex shows a prominent annual variation while the southern vortex shows a clear semi-annual variation as well as annual variation. Thirdly, we found that the total intensity of the L current system changes depending on solar activity and season; seasonal variations of the L current intensity show an enhancement during the December solstice, independent of the level of solar activity. Copyright 2011 by the American Geophysical Union.

  11. Geomagnetic cutoffs: a review for space dosimetry applications.

    PubMed

    Smart, D F; Shea, M A

    1994-10-01

    The earth's magnetic field acts as a shield against charged particle radiation from interplanetary space, technically described as the geomagnetic cutoff. The cutoff rigidity problem (except for the dipole special case) has "no solution in closed form". The dipole case yields the Stormer equation which has been repeatedly applied to the earth in hopes of providing useful approximations of cutoff rigidities. Unfortunately the earth's magnetic field has significant deviations from dipole geometry, and the Stormer cutoffs are not adequate for most applications. By application of massive digital computer power it is possible to determine realistic geomagnetic cutoffs derived from high order simulation of the geomagnetic field. Using this technique, "world-grids" of directional cutoffs for the earth's surface and for a limited number of satellite altitudes have been derived. However, this approach is so expensive and time consuming it is impractical for most spacecraft orbits, and approximations must be used. The world grids of cutoff rigidities are extensively used as lookup tables, normalization points and interpolation aids to estimate the effective geomagnetic cutoff rigidity of a specific location in space. We review the various options for estimating the cutoff rigidity for earth-orbiting satellites.

  12. ISS Plasma Contactor Units Operations During Strong Geomagnetic Activity

    NASA Astrophysics Data System (ADS)

    Alred, J.; Mikatarian, R.; Barsamian, H.; Minow, J.; Koontz, S.

    2003-12-01

    The large structure and high voltage arrays of the ISS represent a complex system that interacts with the Earth's ionosphere. To mitigate spacecraft charging problems on the ISS, two Plasma Contactor Units discharge ionized xenon gas to "clamp" the potential of the ISS with respect to the low Earth orbit plasma. The Plasma Interaction Model, a model of ISS plasma interaction developed from the basic physics of the interaction phenomena, includes magnetic induction effects, plasma temperature and density effects, interaction of the high voltage solar arrays with ionospheric plasma, and accounts for other conductive areas on the ISS. To augment this model, the PCU discharge current has been monitored for the ISS in a variety of flight attitudes as well as during the annual seasons. A review of the PCU discharge currents shows a correlation to the geomagnetic activity. The variation in the PCU discharge current during strong geomagnetic activity will be presented. Also, the PCU discharge currents during periods of low geomagnetic activity will be discussed. The presentation will conclude with a comparison of satellite plasma measurements during different stages of geomagnetic activity.

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

    NASA Astrophysics Data System (ADS)

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

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

  14. The Use of Dispersion Relations For The Geomagnetic Transfer Functions

    NASA Astrophysics Data System (ADS)

    Marcuello, A.; Queralt, P.; Ledo, J. J.

    The magnetotelluric responses are complex magnitudes, where real and imaginary parts contain the same information on the geoelectrical structure. It seems possible, from very general hypotheses on the geoelectrical models (causality, stability and passivity), to apply the Kramers-Krönig dispersion relations to the magnetotelluric responses (impedance, geomagnetic transfer functions,...). In particular, the applica- bility of these relations to the impedance is a current point of discussion, but there are not many examples of their application to the geomagnetic transfer functions (tipper). The aim of this paper is to study how the relations of dispersion are applied to the real and imaginary part of the geomagnetic transfer functions, and to check its validity. For this reason, we have considered data (or responses) from two- and three-dimensional structures, and for these data, we have taken two situations: 1.- Responses that have been synthetically generated from numerical modelling, that allows us to control the quality of the data. 2.- Responses obtained from fieldwork, that are affected by exper- imental error. Additionally, we have also explored the use of these relations to extrap- olate the geomagnetic transfer functions outside the interval of measured frequencies, in order to obtain constrains on the values of these extrapolated data. The results have shown that the dispersion relations are accomplished for the geomag- netic transfer functions, and they can offer information about how these responses are behaved outside (but near) the range of measured frequencies.

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

    PubMed

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

    2004-01-01

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

  16. Statistical Relationship between Sawtooth Oscillations and Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Hun; Lee, Dae-Young; Choi, Cheong-Rim; Her, Young-Tae; Han, Jin-Wook; Hong, Sun-Hak

    2008-06-01

    We have investigated a statistical relationship between sawtooth oscillations and geomagnetic storms during 2000-2004. First of all we selected a total of 154 geomagnetic storms based on the Dst index, and distinguished between different drivers such as Coronal Mass Ejection (CME) and Co-rotating Interaction Region (CIR). Also, we identified a total of 48 sawtooth oscillation events based on geosynchronous energetic particle data for the same 2000-2004 period. We found that out of the 154 storms identified, 47 storms indicated the presence of sawtooth oscillations. Also, all but one sawtooth event identified occurred during a geomagnetic storm interval. It was also found that sawtooth oscillation events occur more frequently for storms driven by CME (˜62%) than for storms driven by CIR (˜30%). In addition, sawtooth oscillations occurred mainly (˜82%) in the main phase of storms for CME-driven storms while they occurred mostly (˜78%) during the storm recovery phase for CIR-driven storms. Next we have examined the average characteristics of the Bz component of IMF, and solar wind speed, which were the main components for driving geomagnetic storm. We found that for most of the sawtooth events, the IMF Bz corresponds to --15 to 0 nT and the solar wind speed was in the range of 400˜700 km/s. We found that there was a weak tendency that the number of teeth for a given sawtooth event interval was proportional to the southward IMF Bz magnitude.

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  18. The risk characteristics of solar and geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Podolska, Katerina

    2016-04-01

    The main aim of this contribution is a deeper analysis of the influence of solar activity which is expected to have an impact on human health, and therefore on mortality, in particular civilization and degenerative diseases. We have constructed the characteristics that represent the risk of solar and geomagnetic activity on human health on the basis of our previous analysis of association between the daily numbers of death on diseases of the nervous system and diseases of the circulatory system and solar and geomagnetic activity in the Czech Republic during the years 1994 - 2013. We used long period daily time series of numbers of deaths by cause, long period time series of solar activity indices (namely R and F10.7), geomagnetic indicies (Kp planetary index, Dst) and ionospheric parameters (foF2 and TEC). The ionospheric parameters were related to the geographic location of the Czech Republic and adjusted for middle geographic latitudes. The risk characteristics were composed by cluster analysis in time series according to the phases of the solar cycle resp. the seasonal insolation at mid-latitudes or the daily period according to the impact of solar and geomagnetic activity on mortality by cause of death from medical cause groups of death VI. Diseases of the nervous system and IX. Diseases of the circulatory system mortality by 10th Revision of International Classification of Diseases WHO (ICD-10).

  19. Investigating dynamical complexity of geomagnetic jerks using various entropy measures

    NASA Astrophysics Data System (ADS)

    Balasis, Georgios; Potirakis, Stelios; Mandea, Mioara

    2016-06-01

    Recently, many novel concepts originated in dynamical systems or information theory have been developed, partly motivated by specific research questions linked to geosciences, and found a variety of different applications. This continuously extending toolbox of nonlinear time series analysis highlights the importance of the dynamical complexity to understand the behavior of the complex Earth's system and its components. Here, we propose to apply such new approaches, mainly a series of entropy methods to the time series of the geomagnetic field. Two datasets provided by Chambon la Foret (France) and Niemegk (Germany) observatories are considered for analysis to detect dynamical complexity changes associated with geomagnetic jerks, the abrupt changes in the second temporal derivative of the Earth's magnetic field. The results clearly demonstrate the ability of Shannon and Tsallis entropies as well as Fisher information to detect events in a regional manner having identified complexities lower than the background in time intervals when geomagnetic jerks have already been reported in the literature. Additionally, these information measures are directly applicable to the original data without having to derive the secular variation or acceleration from the observatory monthly means. The strength of the proposed analysis to reveal dynamical complexity features associated with geomagnetic jerks can be utilized for analyzing not only ground measurements, but also satellite data, as those provided by the current magnetic field mission of Swarm.

  20. An Introduction to Data Assimilation and Predictability in Geomagnetism

    NASA Astrophysics Data System (ADS)

    Fournier, Alexandre; Hulot, Gauthier; Jault, Dominique; Kuang, Weijia; Tangborn, Andrew; Gillet, Nicolas; Canet, Elisabeth; Aubert, Julien; Lhuillier, Florian

    2010-08-01

    Data assimilation in geomagnetism designates the set of inverse methods for geomagnetic data analysis which rely on an underlying prognostic numerical model of core dynamics. Within that framework, the time-dependency of the magnetohydrodynamic state of the core need no longer be parameterized: The model trajectory (and the secular variation it generates at the surface of the Earth) is controlled by the initial condition, and possibly some other static control parameters. The primary goal of geomagnetic data assimilation is then to combine in an optimal fashion the information contained in the database of geomagnetic observations and in the dynamical model, by adjusting the model trajectory in order to provide an adequate fit to the data. The recent developments in that emerging field of research are motivated mostly by the increase in data quality and quantity during the last decade, owing to the ongoing era of magnetic observation of the Earth from space, and by the concurrent progress in the numerical description of core dynamics. In this article we review briefly the current status of our knowledge of core dynamics, and elaborate on the reasons which motivate geomagnetic data assimilation studies, most notably (a) the prospect to propagate the current quality of data backward in time to construct dynamically consistent historical core field and flow models, (b) the possibility to improve the forecast of the secular variation, and (c) on a more fundamental level, the will to identify unambiguously the physical mechanisms governing the secular variation. We then present the fundamentals of data assimilation (in its sequential and variational forms) and summarize the observations at hand for data assimilation practice. We present next two approaches to geomagnetic data assimilation: The first relies on a three-dimensional model of the geodynamo, and the second on a quasi-geostrophic approximation. We also provide an estimate of the limit of the predictability of

  1. Sleep Disturbances in Mood Disorders.

    PubMed

    Rumble, Meredith E; White, Kaitlin Hanley; Benca, Ruth M

    2015-12-01

    The article provides an overview of common and differentiating self-reported and objective sleep disturbances seen in mood-disordered populations. The importance of considering sleep disturbances in the context of mood disorders is emphasized, because a large body of evidence supports the notion that sleep disturbances are a risk factor for onset, exacerbation, and relapse of mood disorders. In addition, potential mechanisms for sleep disturbance in depression, other primary sleep disorders that often occur with mood disorders, effects of antidepressant and mood-stabilizing drugs on sleep, and the adjunctive effect of treating sleep in patients with mood disorders are discussed.

  2. Climate Change and Disturbance Interactions

    NASA Astrophysics Data System (ADS)

    McKenzie, Don; Allen, Craig D.

    2007-05-01

    Workshop on Climate Change and Disturbance Interactions in Western North America, Tucson, Ariz., 12-15 February 2007 Warming temperatures across western North America, coupled with increased drought, are expected to exacerbate disturbance regimes, particularly wildfires, insect outbreaks, and invasions of exotic species. Many ecologists and resource managers expect ecosystems to change more rapidly from disturbance effects than from the effects of a changing climate by itself. A particular challenge is to understand the interactions among disturbance regimes; for example, how will massive outbreaks of bark beetles, which kill drought-stressed trees by feeding on cambial tissues, increase the potential for large severe wildfires in a warming climate?

  3. Empirical evidence for latitude dependence and asymmetry of geomagnetic spatial variation in mainland China

    NASA Astrophysics Data System (ADS)

    Lu, Shikun; Zhang, Hao; Li, Xihai; Liu, Daizhi; Wang, Xiqin

    2016-05-01

    Spatiotemporal geomagnetic variation is a significant research topic of geomagnetism and space physics. Generated by convection and flows within the fluid outer core, latitude dependence and asymmetry, as the inherent spatiotemporal properties of geomagnetic field, have been extensively studied. We apply and modify an extension of existing method, Hidden Markov Model (HMM), which is an efficient tool for modeling the statistical properties of time series. Based on ground magnetic measurement data set in mainland China, first, we find the parameters of HMM can be used as the geomagnetic statistical signature to represent the spatiotemporal geomagnetic variations for each site. The results also support the existence of the geomagnetic latitude dependence more apparently. Furthermore, we provide solid empirical evidence for geomagnetic asymmetry relying on such ground magnetic measurement data set.

  4. On the Possibilities of Predicting Geomagnetic Secular Variation with Geodynamo Modeling

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  5. Arabidopsis thaliana root elongation growth is sensitive to lunisolar tidal acceleration and may also be weakly correlated with geomagnetic variations

    PubMed Central

    Barlow, Peter W.; Fisahn, Joachim; Yazdanbakhsh, Nima; Moraes, Thiago A.; Khabarova, Olga V.; Gallep, Cristiano M.

    2013-01-01

    Background Correlative evidence suggests a relationship between the lunisolar tidal acceleration and the elongation rate of arabidopsis roots grown under free-running conditions of constant low light. Methods Seedlings of Arabidopsis thaliana were grown in a controlled-climate chamber maintained at a constant temperature and subjected to continuous low-level illumination from fluorescent tubes, conditions that approximate to a ‘free-running’ state in which most of the abiotic factors that entrain root growth rates are excluded. Elongation of evenly spaced, vertical primary roots was recorded continuously over periods of up to 14 d using high temporal- and spatial-resolution video imaging and were analysed in conjunction with geophysical variables. Key Results and Conclusions The results confirm the lunisolar tidal/root elongation relationship. Also presented are relationships between the hourly elongation rates and the contemporaneous variations in geomagnetic activity, as evaluated from the disturbance storm time and ap indices. On the basis of time series of root elongation rates that extend over ≥4 d and recorded at different seasons of the year, a provisional conclusion is that root elongation responds to variation in the lunisolar force and also appears to adjust in accordance with variations in the geomagnetic field. Thus, both lunisolar tidal acceleration and the geomagnetic field should be considered as modulators of root growth rate, alongside other, stronger and more well-known abiotic environmental regulators, and perhaps unexplored factors such as air ions. Major changes in atmospheric pressure are not considered to be a factor contributing to oscillations of root elongation rate. PMID:23532042

  6. The High-Risk (Disturbed and Disturbing) College Student

    ERIC Educational Resources Information Center

    Hollingsworth, Kathy R.; Dunkle, John H.; Douce, Louise

    2009-01-01

    The disturbed and disturbing college student causes the most vexing concerns for student affairs administrators. The Assessment-Intervention of Student Problems (AISP) model offers a useful and easily understood framework for dealing with the various challenges of this high-risk student population. This chapter focuses on changes that have…

  7. Geomagnetic Storms and Acute Myocardial Infarctions Morbidity in Middle Latitudes

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    Results of collaborative studies on revealing a possible relationship between solar activity (SA) and geomagnetic activity (GMA) and pre-hospital acute myocardial infarction (AMI) morbidity are presented. Studies were based on medical data from Bulgaria and Azerbaijan. Bulgarian data, covering the period from 01.12.1995 to 31.12.2004, concerned daily distribution of number of patients with AMI diagnose (in total 1192 cases) from Sofia Region on the day of admission at the hospital. Azerbaijani data contained 4479 pre-hospital AMI incidence cases for the period 01.01.2003-31.12.2005 and were collected from 21 emergency and first medical aid stations in Grand Baku Area (including Absheron Economical Region with several millions of inhabitants). Data were "cleaned" as much as possible from social and other factors and were subjected to medical and mathematical/statistical analysis. Medical analysis showed reliability of the used data. Method of ANalysis Of VAriance (ANOVA) was applied to check the significance of GMA intensity effect and the type of geomagnetic storms - those caused by magnetic clouds (MC) and by high speed solar wind streams (HSSWS) - on AMI incidences. Relevant correlation coefficients were calculated. Results were outlined for both considered data. Results obtained for the Sofia data showed statistically significant positive correlation between considered GMA indices and AMI occurrence. ANOVA revealed that AMI incidence number was significantly increased from the day before till the day after geomagnetic storms with different intensities. Geomagnetic storms caused by MC were related to significant increase of AMI number in comparison with the storms caused by HSSWS. There was a trend for such different effects even on -1st and +1st day for the period 1995-2004. Results obtained for the Baku data revealed trends similar to those obtained for Sofia data. AMI morbidity increment was observed on the days with higher GMA intensity and after these days

  8. Some characteristics of large-scale travelling ionospheric disturbances and a relationship between the F2 layer height rises of these disturbances and equatorial pre-sunrise events

    NASA Astrophysics Data System (ADS)

    Bowman, G. G.; Mortimer, I. K.

    2010-07-01

    Initially some characteristics of large-scale travelling ionospheric disturbances (LS-TIDs) have been discussed briefly particularly as reported in the early literature. These discussions also involve the literature on the generation of LS-TIDs at times of geomagnetic bays. Secondly, the possibility that LS-TIDs may be responsible for the F2 layer equatorial pre-sunrise height rises is investigated. Tabulations at hourly intervals of h'F at Huancayo and Washington for a Rz max period (1957-1960) have been used to identify height rises. For a three-hour interval at Huancayo h'F levels equal to or greater than 40 km of medians are used to identify the pre-sunrise height rises. Also height rises at Washington, which occurred earlier than those at Huancayo, have been considered for evidence of travelling disturbances. For 40 events analysed using geomagnetic bays and Washington height rises, a few hours before they occur at Huancayo, indicate the statistical significance of an association with LS-TIDs. Similar results of statistical significance have been obtained using Washington events and bays on average 34 h before 46 Huancayo events. These delays ranged from 29 h to 38 h. The results indicate that bays which occur the day before are responsible for LS-TIDs which encircle the earth.

  9. Ionospheric disturbance dynamo

    SciTech Connect

    Blanc, M.; Richmond, A.D.

    1980-04-01

    A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes.

  10. Autonomic disturbances in narcolepsy.

    PubMed

    Plazzi, Giuseppe; Moghadam, Keivan Kaveh; Maggi, Leonardo Serra; Donadio, Vincenzo; Vetrugno, Roberto; Liguori, Rocco; Zoccoli, Giovanna; Poli, Francesca; Pizza, Fabio; Pagotto, Uberto; Ferri, Raffaele

    2011-06-01

    Narcolepsy is a clinical condition characterized mainly by excessive sleepiness and cataplexy. Hypnagogic hallucinations and sleep paralysis complete the narcoleptic tetrad; disrupted night sleep, automatic behaviors and weight gain are also usual complaints. Different studies focus on autonomic changes or dysfunctions among narcoleptic patients, such as pupillary abnormalities, fainting spells, erectile dysfunction, night sweats, gastric problems, low body temperature, systemic hypotension, dry mouth, heart palpitations, headache and extremities dysthermia. Even if many studies lack sufficient standardization or their results have not been replicated, a non-secondary involvement of the autonomic nervous system in narcolepsy is strongly suggested, mainly by metabolic and cardiovascular findings. Furthermore, the recent discovery of a high risk for overweight and for metabolic syndrome in narcoleptic patients represents an important warning for clinicians in order to monitor and follow them up for their autonomic functions. We review here studies on autonomic functions and clinical disturbances in narcoleptic patients, trying to shed light on the possible contribute of alterations of the hypocretin system in autonomic pathophysiology.

  11. The response of local power grid at low-latitude to geomagnetic storm: An application of the Hilbert Huang transform

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Wang, Chuan-Bing; Liu, Lu; Sun, Wei-Huai

    2016-04-01

    The Hilbert-Huang transform (HHT) is an adaptive data analysis method that can accommodate the variety of data generated by nonlinear and nonstationary processes in nature. In this paper, we focus on the small geomagnetically induced current (GIC) at the local substations in low-latitude power grid of China, responding to a moderate storm on 14-18 July 2012. The HHT is applied to analyze the neutral point currents (NPCs) of transformers measured at different substations, and the GIC indices converted from local geomagnetic field measurements. The original data are decomposed into intrinsic mode functions (IMFs) using the ensemble empirical mode decomposition. After removal of the quasi-diurnal components related with the solar quiet variation, the IMFs representing storm disturbances are transformed into Hilbert energy spectra. The results show that some transformers have more or less responses to the moderate storm in the form of Hilbert energy spectra with the frequency around 2-3 mHz. A comparison on the amplitude changes of the spectra total energy of NPCs' perturbation during storm time intervals at different sites suggests that a shell type of three-phase single transformer group seems to be more vulnerable in the storm. Although the low-latitude power grids usually show very small GIC, these can be used to investigate the potential risk of space weather to the system.

  12. Density duct formation in the wake of a travelling ionospheric disturbance: Murchison Widefield Array observations

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Cairns, Iver H.; Murphy, Tara; Erickson, Philip J.; Bell, Martin E.; Rowlinson, Antonia; Arora, Balwinder Singh; Morgan, John; Ekers, Ronald D.; Hurley-Walker, Natasha; Kaplan, David L.

    2016-02-01

    Geomagnetically aligned density structures with a range of sizes exist in the near-Earth plasma environment, including 10-100 km wide VLF/HF wave-ducting structures. Their small diameters and modest density enhancements make them difficult to observe, and there is limited evidence for any of the several formation mechanisms proposed to date. We present a case study of an event on 26 August 2014 where a travelling ionospheric disturbance (TID) shortly precedes the formation of a complex collection of field-aligned ducts, using data obtained by the Murchison Widefield Array (MWA) radio telescope. Their spatiotemporal proximity leads us to suggest a causal interpretation. Geomagnetic conditions were quiet at the time, and no obvious triggers were noted. Growth of the structures proceeds rapidly, within 0.5 h of the passage of the TID, attaining their peak prominence 1-2 h later and persisting for several more hours until observations ended at local dawn. Analyses of the next 2 days show field-aligned structures to be preferentially detectable under quiet rather than active geomagnetic conditions. We used a raster scanning strategy facilitated by the speed of electronic beamforming to expand the quasi-instantaneous field of view of the MWA by a factor of 3. These observations represent the broadest angular coverage of the ionosphere by a radio telescope to date.

  13. Subclassification of School Phobic Disturbances.

    ERIC Educational Resources Information Center

    Atkinson, Leslie; And Others

    The confusion surrounding all aspects of school refusal may rest partly on the misguided assumption that the disturbance represents a single syndrome. Five consistently emerging variables which may help distinguish among school phobic types were abstracted from the literature: extensiveness of disturbance, mode of onset, age, fear source, and…

  14. Educating Emotionally Disturbed Children: Readings.

    ERIC Educational Resources Information Center

    Dupont, Henry, Ed.

    Designed to introduce the classroom teacher to a clinical teaching approach with the emotionally disturbed child and to encourage critical discussion of current practices and theories, the collection of readings presents selected dimensions of emotional disturbance such as personality patterns, learning disabilities, and minimal brain damage.…

  15. Complexity signatures in the geomagnetic H component recorded by the Tromsø magnetometer (70° N, 19° E) over the last ¼ century

    NASA Astrophysics Data System (ADS)

    Hall, C. M.

    2014-05-01

    Solar disturbances, depending on the orientation of the interplanetary magnetic field, typically result in perturbations of the geomagnetic field as observed by magnetometers on the ground. Here, the geomagnetic field's horizontal component, as measured by the ground-based observatory-standard magnetometer at Tromsø (70° N, 19° E) is examined for signatures of complexity. 25 year-long 10 s resolution datasets are analysed, but for fluctuations with timescales less than 1 day. Quantile-quantile (Q-Q) plots are employed first, revealing the fluctuations are better represented by Cauchy rather than Gaussian distributions. Thereafter, both spectral density and detrended fluctuation analysis methods are used to estimate values of the generalized Hurst exponent, α. The results are then compared with independent findings. Inspection and comparison of the spectral and detrended fluctuation analyses reveals that timescales between 1 h and 1 d are characterized by fractional Brownian motion with a generalized Hurst exponent of ~1.4 whereas including timescales as short as 1 min suggests fractional Brownian motion with a generalized Hurst exponent of ~1.6. This is consistent with changes in the position of the auroral electrojet that can be considered rapid during the course of an evening, whereas from minute-to-minute the electrojet moves more persistently in geomagnetic latitude.

  16. Effects of solar and geomagnetic activities on the sub-ionospheric very low frequency transmitter signals received by the DEMETER micro-satellite

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Yahia; Schwingenschuh, Konrad; Al-Haddad, Emad; Parrot, Michel; Galopeau, Patrick H. M.; Besser, Bruno; Stangl, Guenter; Voller, Wolfgang

    2012-04-01

    In the framework of seismic precursor electromagnetic investigations, we analyzed the very low frequency (VLF) amplitude signals recorded by the Instrument Champ Electrique (ICE) experiment on board the DEMETER micro-satellite. The sun-synchronous orbits of the micro-satellite allowed us to cover an invariant latitude of between -65° and +65° in a time interval of about 40 min. We considered four transmitter signals emitted by stations in Europe (France, FTU, 18.3 kHz; Germany, DFY, 16.58 kHz),Asia (Japan, JP, 17.8 kHz) and Australia (Australia, NWC, 19.8 kHz). We studied the variations of these VLF signals, taking into consideration: the signal-to-noise ratio, sunspots, and the geomagnetic activity. We show that the degree of correlation in periods of high geomagnetic and solar activities is, on average, about 40%. Such effects can be fully neglected in the period of weak activity. We also find that the solar activity can have a more important effect on the VLF transmitter signal than the geomagnetic activity. Our data are combined with models where the coupling between the lithosphere, atmosphere and ionosphere is essential to explain how ionospheric disturbances scatter the VLF transmitter signal.

  17. Ionospheric current source modeling and global geomagnetic induction using ground geomagnetic observatory data

    USGS Publications Warehouse

    Sung, Joyce; Kelbert, Anna; Egbert, G.D.

    2015-01-01

    Long-period global-scale electromagnetic induction studies of deep Earth conductivity are based almost exclusively on magnetovariational methods and require accurate models of external source spatial structure. We describe approaches to inverting for both the external sources and three-dimensional (3-D) conductivity variations and apply these methods to long-period (T≥1.2 days) geomagnetic observatory data. Our scheme involves three steps: (1) Observatory data from 60 years (only partly overlapping and with many large gaps) are reduced and merged into dominant spatial modes using a scheme based on frequency domain principal components. (2) Resulting modes are inverted for corresponding external source spatial structure, using a simplified conductivity model with radial variations overlain by a two-dimensional thin sheet. The source inversion is regularized using a physically based source covariance, generated through superposition of correlated tilted zonal (quasi-dipole) current loops, representing ionospheric source complexity smoothed by Earth rotation. Free parameters in the source covariance model are tuned by a leave-one-out cross-validation scheme. (3) The estimated data modes are inverted for 3-D Earth conductivity, assuming the source excitation estimated in step 2. Together, these developments constitute key components in a practical scheme for simultaneous inversion of the catalogue of historical and modern observatory data for external source spatial structure and 3-D Earth conductivity.

  18. Western Disturbances: A review

    NASA Astrophysics Data System (ADS)

    Dimri, A. P.; Niyogi, D.; Barros, A. P.; Ridley, J.; Mohanty, U. C.; Yasunari, T.; Sikka, D. R.

    2015-06-01

    Cyclonic storms associated with the midlatitude Subtropical Westerly Jet (SWJ), referred to as Western Disturbances (WDs), play a critical role in the meteorology of the Indian subcontinent. WDs embedded in the southward propagating SWJ produce extreme precipitation over northern India and are further enhanced over the Himalayas due to orographic land-atmosphere interactions. During December, January, and February, WD snowfall is the dominant precipitation input to establish and sustain regional snowpack, replenishing regional water resources. Spring melt is the major source of runoff to northern Indian rivers and can be linked to important hydrologic processes from aquifer recharge to flashfloods. Understanding the dynamical structure, evolution-decay, and interaction of WDs with the Himalayas is therefore necessary to improve knowledge which has wide ranging socioeconomic implications beyond short-term disaster response including cold season agricultural activities, management of water resources, and development of vulnerability-adaptive measures. In addition, WD wintertime precipitation provides critical mass input to existing glaciers and modulates the albedo characteristics of the Himalayas and Tibetan Plateau, affecting large-scale circulation and the onset of the succeeding Indian Summer Monsoon. Assessing the impacts of climate variability and change on the Indian subcontinent requires fundamental understanding of the dynamics of WDs. In particular, projected changes in the structure of the SWJ will influence evolution-decay processes of the WDs and impact Himalayan regional water availability. This review synthesizes past research on WDs with a perspective to provide a comprehensive assessment of the state of knowledge to assist both researchers and policymakers, and context for future research.

  19. Multi-spacecraft testing of time-dependent interplanetary MHD models for operational forecasting of geomagnetic storms

    NASA Technical Reports Server (NTRS)

    Dryer, M.; Smith, Z. K.

    1989-01-01

    An MHD 2-1/2D, time-dependent model is used, together with observations of six solar flares during February 3-7, 1986, to demonstrate global, large-scale, compound disturbances in the solar wind over a wide range of heliolongitudes. This scenario is one that is likely to occur many times during the cruise, possibly even encounter, phases of the Multi-Comet Mission. It is suggested that a model such as this one should be tested with multi-spacecraft data (such as the MCM and earth-based probes) with several goals in view: (1) utility of the model for operational real-time forecasting of geomagnetic storms, and (2) scientific interpretation of certain forms of cometary activities and their possible association with solar-generated activity.

  20. Geomagnetic modification of the mid-latitude ionosphere - Toward a strategy for the improved forecasting of f0F2

    SciTech Connect

    Wrenn, G.L.; Rodger, A.S.

    1989-02-01

    An approach for modeling and forecasting the interspatial critical frequency (f0F2) at quiet and disturbed times is outlined. Statistical analyses of ionosonde data from the Argentine Islands (65 deg S) are used to define patterns for the main phase effects of midlatitude ionospheric storms. Extended to a number of stations, these could be incorporated into algorithms to permit the forecasting of maximum usable frequency for a few hours ahead and enhance the frequency management of shortwave radio communication, especially during a geomagnetic storm. Data from a complete solar cycle, 1971-1981, are used to determine the errors in the forecasts and to demonstrate that a useful advantage can be attained by this method. The rms error in f0F2 for 90,175 samples is 15.6 percent, which compares favorably with those obtained using forecasts based on quiet time values (20.4 percent) or the previous day's measurements (18 percent). 12 references.

  1. Empirical regional models for the short-term forecast of M3000F2 during not quiet geomagnetic conditions over Europe

    NASA Astrophysics Data System (ADS)

    Pietrella, Marco

    An empirical regional model for the prediction of the monthly median field of M3000F2 over Europe (indicated as RM_M3000F2) was developed. Thanks to the IFELM_foF2 models, that are able to provide short-term forecasts of the critical frequency of the F2 layer (foF2 _{STF}) up to three hours in advance, it was possible to considerer the Brudley-Dudeney algorithm as a function of foF2 _{STF} to correct RM_M3000F2 and thus obtaining an empirical regional model for the short-term forecasting of M3000F2 (indicated as RM_M3000F2_BD) up to three hours in advance under not quiet geomagnetic conditions. From the long-term predictions of M3000F2 provided by the IRI model, an empirical regional model for the forecast of the monthly median field of M3000F2 over Europe (indicated as IRI_RM_M3000F2) was derived. IRI_RM_M3000F2 predictions were modified with the Bradley-Dudeney correction factor and another empirical regional model for the short-term forecasting of M3000F2 (indicated as IRI_RM_M3000F2_BD) up to three hours ahead under not quiet geomagnetic conditions was obtained. The main results achieved comparing the performance of RM_M3000F2, RM_M3000F2_BD, IRI_RM_M3000F2, and IRI_RM_M3000F2_BD are: (1) in case of moderate geomagnetic activity, the Bradley-Dudeney correction factor does not improve significantly the predictions; 2) under disturbed geomagnetic conditions, the Bradley-Dudeney formula improves the predictions of RM_M3000F2 in all the European area; (3) in case of very disturbed geomagnetic conditions, Bradley-Dudeney algorithm is very effective in improving the performance of IRI_RM_M3000F2; (4) the forecasting maps originated by RM_M3000F2, RM_M3000F2_BD, and IRI_RM_M3000F2_BD, show some regions where the forecasts are not satisfactory, but also wide sectors where the M3000F2 forecasts quite faithfully match the M3000F2 observations, and therefore the proposed models could be exploited to produce short-term forecasting maps of M3000F2 over Europe up to 3 hours

  2. Steady induction effects in geomagnetism. Part 1C: Geomagnetic estimation of steady surficial core motions: Application to the definitive geomagnetic reference field models

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.

    1993-01-01

    In the source-free mantle/frozen-flux core magnetic earth model, the non-linear inverse steady motional induction problem was solved using the method presented in Part 1B. How that method was applied to estimate steady, broad-scale fluid velocity fields near the top of Earth's core that induce the secular change indicated by the Definitive Geomagnetic Reference Field (DGRF) models from 1945 to 1980 are described. Special attention is given to the derivation of weight matrices for the DGRF models because the weights determine the apparent significance of the residual secular change. The derived weight matrices also enable estimation of the secular change signal-to-noise ratio characterizing the DGRF models. Two types of weights were derived in 1987-88: radial field weights for fitting the evolution of the broad-scale portion of the radial geomagnetic field component at Earth's surface implied by the DGRF's, and general weights for fitting the evolution of the broad-scale portion of the scalar potential specified by these models. The difference is non-trivial because not all the geomagnetic data represented by the DGRF's constrain the radial field component. For radial field weights (or general weights), a quantitatively acceptable explication of broad-scale secular change relative to the 1980 Magsat epoch must account for 99.94271 percent (or 99.98784 percent) of the total weighted variance accumulated therein. Tolerable normalized root-mean-square weighted residuals of 2.394 percent (or 1.103 percent) are less than the 7 percent errors expected in the source-free mantle/frozen-flux core approximation.

  3. Plasmasphere Refilling After Geomagnetic Storms Observed by EMMA Magnetometer Network

    NASA Astrophysics Data System (ADS)

    Del Corpo, A.; Vellante, M.; Heilig, B.; Lichtenberger, J.; Reda, J.; Pietropaolo, E.; Chi, P. J.

    2015-12-01

    We present the results of a study of plasmasphere dynamics during a few geomagnetic storms through examination of radial profiles of the equatorial plasma mass density. The plasma mass density is derived from field line resonance (FLR) frequencies observations across EMMA, a meridional network of 25 magnetometer stations extending from Central Italy to North Finland (1.5 < L < 6.5). The study focuses on plasmaspheric refilling following depletion due to geomagnetic activity. From the time variation of the equatorial plasma mass density we derived daytime refilling rates and the corresponding upward plasma fluxes from the ionosphere for different L-values. Daily averaged refilling rates occurring during the recovery phase have been also investigated.

  4. The geomagnetic secular variation S parameter: A mathematical artifact

    NASA Astrophysics Data System (ADS)

    Linder, J. M.; Gilder, S. A.

    2011-12-01

    Secular variation, the change in the Earth's magnetic field through time, reflects the energy state of the geodynamo. Secular variation is commonly quantified by the standard deviation of the angular distances of the virtual geomagnetic poles to their mean pole, known as the S value. The S value has long been thought to exhibit latitude dependence [S(λ)] whose origin is widely attributed to a combination of time-varying dipole and non-dipole components. The slope, magnitude and uncertainty of S(λ) are taken as a basis to model the geomagnetic field and understand its evolution. Here we show that variations in S stem from a mathematical aberration of the conversion from directions to poles. A new method to quantify secular variation is proposed.

  5. Low-altitude trapped protons at the geomagnetic equator

    NASA Technical Reports Server (NTRS)

    Guzik, T. G.; Miah, M. A.; Mitchell, J. M.; Wefel, J. P.

    1989-01-01

    Geomagnetically trapped protons in the 0.6- to 9-MeV energy range were measured at latitudes near the geomagnetic equator by the Phoenix 1 experiment on board the S81-1 mission from May to November 1982. The protons show a distribution in latitude along the line of minimum magnetic field strength with a full width at half maximum of about 10 deg but with no appreciable longitudinal variation. Between 170 and 290 Km the peak proton flux shows a fifth-power altitude dependence, in contrast to previous measurements at higher altitudes, possibly demonstrating source attenuation. The efficiency of the telescope is calculated as a function of particle pitch angle and used to investigate the time dependence (1969-1982) of the intensity.

  6. De-noising Diurnal Variation Data in Geomagnetic Field Modelling

    NASA Astrophysics Data System (ADS)

    Onovughe, E.

    2017-01-01

    Ground based geomagnetic observatory series have been used to investigate and describe the residuals between a continuous geomagnetic field model and observed diurnal variation for noise-removal of signal due to external field of magnetospheric ring current sources. In all the observatories studied, the residuals in the X-direction consistently show the noisiest signal. Results show that the residuals in the X-direction correlates closely with the RC-index, suggesting an origin from unmodelled external field variation. Notable cross-correlation is also seen between the residuals and the RC-index at zero-lag. Removal/reduction of this unmodelled signal enhances resolution of fine-scale detail in diurnal variation studies.

  7. High-latitude geomagnetic studies (22-23 millihertz)

    SciTech Connect

    Wolfe, A. City Univ. of New York, Brooklyn ); Lanzerotti, L.J.; Maclennan, C.C.; Medford, L.V. )

    1988-01-01

    Geomagnetic field measurements were initiated at Iqaluit (formerly Frobisher Bay) in the Northwest Territories of Canada during July 1985 (Wolfe et al. 1986). This site was selected because it was calculated to be in the conjugate area to the Amundsen-Scott South Pole Station where extensive geomagnetic research has been conducted. The principal scientific objectives are to study the conjugacy of high-latitude magnetic fluctuations observed at Iqaluit and South Pole (L{approximately}13). In this report, the authors extend the previous report of Wolfe et al. (1987) and comment upon the conjugacy of the stations for magnetic field fluctuations in the Pc3 (22-33 millihertz) hydromagnetic regime and upon the penetration of hydromagnetic energy deeper into the magnetosphere on the local dayside.

  8. Acceleration and loss of relativistic electrons during small geomagnetic storms

    DOE PAGES

    Anderson, B. R.; Millan, R. M.; Reeves, G. D.; ...

    2015-12-02

    We report that past studies of radiation belt relativistic electrons have favored active storm time periods, while the effects of small geomagnetic storms (Dst >₋50 nT) have not been statistically characterized. In this timely study, given the current weak solar cycle, we identify 342 small storms from 1989 through 2000 and quantify the corresponding change in relativistic electron flux at geosynchronous orbit. Surprisingly, small storms can be equally as effective as large storms at enhancing and depleting fluxes. Slight differences exist, as small storms are 10% less likely to result in flux enhancement and 10% more likely to result inmore » flux depletion than large storms. Nevertheless, it is clear that neither acceleration nor loss mechanisms scale with storm drivers as would be expected. Small geomagnetic storms play a significant role in radiation belt relativistic electron dynamics and provide opportunities to gain new insights into the complex balance of acceleration and loss processes.« less

  9. Acceleration and loss of relativistic electrons during small geomagnetic storms

    SciTech Connect

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

    2015-12-02

    We report that past studies of radiation belt relativistic electrons have favored active storm time periods, while the effects of small geomagnetic storms (Dst >₋50 nT) have not been statistically characterized. In this timely study, given the current weak solar cycle, we identify 342 small storms from 1989 through 2000 and quantify the corresponding change in relativistic electron flux at geosynchronous orbit. Surprisingly, small storms can be equally as effective as large storms at enhancing and depleting fluxes. Slight differences exist, as small storms are 10% less likely to result in flux enhancement and 10% more likely to result in flux depletion than large storms. Nevertheless, it is clear that neither acceleration nor loss mechanisms scale with storm drivers as would be expected. Small geomagnetic storms play a significant role in radiation belt relativistic electron dynamics and provide opportunities to gain new insights into the complex balance of acceleration and loss processes.

  10. Earth orientation parameters: excitation by atmosphere, oceans and geomagnetic jerks

    NASA Astrophysics Data System (ADS)

    Vondrak, Jan; Ron, Cyril

    2015-08-01

    It is well known that geophysical fluids (atmosphere, oceans) excite Earth orientation. The influence is known to be dominant for polar motion, partly responsible for length-of-day changes, and very small effects are now observable also in nutation. Very recently several authors (Holme and de Viron 2005, Gibert and le Mouel 2008, Malkin 2013) noted that sudden changes of Earth's speed of rotation and phase/amplitude of the free motions of its spin axis (Chandler wobble, Free core nutation) occur near the epochs of geomagnetic jerks (GMJ - rapid changes of the secular variations of geomagnetic field). By using the numerical integration of broad-band Liouville equations (Brzezinski 1994) we demonstrate that if non-periodical bell-like excitations of limited length (app. 1 year) around the epochs of GMJ are added to atmospheric and oceanic excitations, the agreement between observed and calculated Earth orientation parameters is improved significantly.

  11. Relationships between Geomagnetic Induced Currents and Field Aligned Currents

    NASA Astrophysics Data System (ADS)

    Waters, C. L.; Barnett, R.; Anderson, B. J.; Gjerloev, J. W.; Korth, H.; Barnes, R. J.

    2015-12-01

    Geomagnetic Induced Currents (GICs) appear in the ground due to time varying magnetic fields that occur during periods of enhanced geomagnetic activity. The resultant time varying electric fields at Earth's surface drive very low frequency, currents through electricity supply transformers which reduces transforming capacity. In extreme cases, electricity supply grids can collapse as multiple transformers are affected. GICs have larger magnitudes at auroral latitudes and should be related to the field aligned current (FAC) and auroral ionosphere currents systems. At ground locations under the regions between upward and downward FACs, the GIC related fields show a direct relationship with the time derivative of the FACs. This allows a conversion factor between FAC and GIC magnitudes. Examples of the relationship between FAC and GIC related fields are presented using data derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) and SuperMAG.

  12. Modeling Longitudinal Hemispheric Differences during Geomagnetic Storm Times

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  13. Longitudinal Hemispheric Differences During Geomagnetic Storm Times Examined with GITM

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Work by Immel and Mannucci [2013] has indicated that geomagnetic storms cause larger effects on the ionospheric TEC (Total Electron Count) in the American sector than anywhere else on the planet, suggesting that there is a longitude dependent (UT) effect which is important for correctly understanding the impact, structure and timing of geomagnetic storms. Using Global Ionosphere-Thermosphere Model (GITM) [Ridley et al., 2006] coupled with realistic transport, we examine the underlying mechanisms of the longitude-dependent storm enhancements. We accomplish this by using a case study storm observed on 5 August 2011 and then conducting model experiments with GITM by shifting the storm onset time over the course of 24 hours. TEC measurements, the Dst index, and IMF are used in conjunction with model output.

  14. Solar wind control of auroral zone geomagnetic activity

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  15. Transient cosmic ray increase associated with a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Kudo, S.; Wada, M.; Tanskanen, P.; Kodama, M.

    1985-01-01

    On the basis of worldwide network data of cosmic ray nucleonic components, the transient cosmic ray increase due to the depression of cosmic ray cutoff rigidity during a severe geomagnetic storm was investigated in terms of the longitudinal dependence. Multiple correlation analysis among isotropic and diurnal terms of cosmic ray intensity variations and Dst term of the geomagnetic field is applied to each of various station's data. It is shown that the amplitude of the transient cosmic ray increase associated with Dst depends on the local time of the station, and that its maximum phase is found in the evening sector. This fact is consistent with the theoretical estimation based on the azimuthally asymmetric ring current model for the magnetic DS field.

  16. MHD-waves in the geomagnetic tail: A review

    NASA Astrophysics Data System (ADS)

    Leonovich, Anatoliy; Mazur, Vitaliy; Kozlov, Daniil

    2015-03-01

    This article presents the review of experimental and theoretical studies on ultra-lowfrequency MHD oscillations of the geomagnetic tail. We consider the Kelvin-Helmholtz instability at the magnetopause, oscillations with a discrete spectrum in the "magic frequencies"range, the ballooning instability of coupled Alfvén and slow magnetosonic waves, and "flapping" oscillations of the current sheet of the geomagnetic tail. Over the last decade, observations from THEMIS, CLUSTER and Double Star satellites have been of great importance for experimental studies. The use of several spacecraft allows us to study the structure of MHD oscillations with high spatial resolution. Due to this, we can make a detailed comparison between theoretical results and those obtained from multi-spacecraft studies. To make such comparisons in theoretical studies, in turn, we have to use the numerical models closest to the real magnetosphere.

  17. International Geomagnetic Reference Field: the 12th generation

    NASA Astrophysics Data System (ADS)

    Thébault, Erwan; Finlay, Christopher C.; Beggan, Ciarán D.; Alken, Patrick; Aubert, Julien; Barrois, Olivier; Bertrand, Francois; Bondar, Tatiana; Boness, Axel; Brocco, Laura; Canet, Elisabeth; Chambodut, Aude; Chulliat, Arnaud; Coïsson, Pierdavide; Civet, François; Du, Aimin; Fournier, Alexandre; Fratter, Isabelle; Gillet, Nicolas; Hamilton, Brian; Hamoudi, Mohamed; Hulot, Gauthier; Jager, Thomas; Korte, Monika; Kuang, Weijia; Lalanne, Xavier; Langlais, Benoit; Léger, Jean-Michel; Lesur, Vincent; Lowes, Frank J.; Macmillan, Susan; Mandea, Mioara; Manoj, Chandrasekharan; Maus, Stefan; Olsen, Nils; Petrov, Valeriy; Ridley, Victoria; Rother, Martin; Sabaka, Terence J.; Saturnino, Diana; Schachtschneider, Reyko; Sirol, Olivier; Tangborn, Andrew; Thomson, Alan; Tøffner-Clausen, Lars; Vigneron, Pierre; Wardinski, Ingo; Zvereva, Tatiana

    2015-05-01

    The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth's magnetic field.

  18. The International Geomagnetic Reference Field: the twelfth generation

    NASA Astrophysics Data System (ADS)

    Thebault, Erwan; Finlay, Christopher; The IGRF Working Group

    2015-04-01

    The IGRF is an internationally-agreed reference model of the Earth's magnetic field produced under the auspices of the International Association of Geomagnetism and Aeronomy. The IGRF-12 is the latest update of this well-known model which is used each year by many thousands of users for both industrial and scientific purposes. In October 2014, ten institutions worldwide have made contributions to the IGRF. These models were evaluated and the twelfth generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014. In this presentation, we will report on the IGRF activities, briefly describe the candidate models, summarize the evaluation of models performed by different independent teams, show how the IGRF-12 models were calculated and finally discuss some of the main magnetic features of this new model.

  19. Geomagnetic Observatory Data for Real-Time Applications

    NASA Astrophysics Data System (ADS)

    Love, J. J.; Finn, C. A.; Rigler, E. J.; Kelbert, A.; Bedrosian, P.

    2015-12-01

    The global network of magnetic observatories represents a unique collective asset for the scientific community. Historically, magnetic observatories have supported global magnetic-field mapping projects and fundamental research of the Earth's interior and surrounding space environment. More recently, real-time data streams from magnetic observatories have become an important contributor to multi-sensor, operational monitoring of evolving space weather conditions, especially during magnetic storms. In this context, the U.S. Geological Survey (1) provides real-time observatory data to allied space weather monitoring projects, including those of NOAA, the U.S. Air Force, NASA, several international agencies, and private industry, (2) collaborates with Schlumberger to provide real-time geomagnetic data needed for directional drilling for oil and gas in Alaska, (3) develops products for real-time evaluation of hazards for the electric-power grid industry that are associated with the storm-time induction of geoelectric fields in the Earth's conducting lithosphere. In order to implement strategic priorities established by the USGS Natural Hazards Mission Area and the National Science and Technology Council, and with a focus on developing new real-time products, the USGS is (1) leveraging data management protocols already developed by the USGS Earthquake Program, (2) developing algorithms for mapping geomagnetic activity, a collaboration with NASA and NOAA, (3) supporting magnetotelluric surveys and developing Earth conductivity models, a collaboration with Oregon State University and the NSF's EarthScope Program, (4) studying the use of geomagnetic activity maps and Earth conductivity models for real-time estimation of geoelectric fields, (5) initiating geoelectric monitoring at several observatories, (6) validating real-time estimation algorithms against historical geomagnetic and geoelectric data. The success of these long-term projects is subject to funding constraints

  20. Geomagnetic Activity and the Equatorial Scintillation of Satellite Signals.

    DTIC Science & Technology

    1980-05-19

    BEORE COMPLETING FORM i. �T NUMBER 2 GOVT ACCESSION No. 3 . RECIPIENT’S CATALOG NUMBER NOSC Technical Report 554 (TR 554) /. 4. TITLE (and SW 441111...Occurrence and intensity of equatorial scintillation have been correlated with daily summed geomagnetic 3 -hour Kp indices, through scintillation data from...satellites at two elevation angles for uhf and 1--hand. They also have been correlated with the individual 3 -hour Kp indices and the correlations

  1. An Impending geomagnetic transition? Hints from the past

    NASA Astrophysics Data System (ADS)

    Laj, Carlo; Kissel, Catherine

    2016-04-01

    The rapid decrease of the geomagnetic field intensity in the last centuries together with a growth of the South Atlantic Anomaly has led to speculations that an attempt to a reversal or an excursion might be under way. Here we investigate this hypothesis by examining past records of geomagnetic field intensity obtained from sedimentary cores and from the study of cosmogenic nuclides. The selected records describe geomagnetic changes with an unprecedented temporal resolution between 20 and 75 kyr B.P. The precise age model and the accurate calibration of intensities on absolute scale allow to calculate the duration and the rate of change of the field during the well documented excursions of Laschamp and Mono Lake. The rate of decay of the field intensity during these excursions is is virtually similar to that observed over the last few centuries and much higher than that observed for other low intensity periods of the same duration but not associated to any polarity change. Although these records do not provide undisputable information on future evolution of the field, we find that some aspects of the present-day geomagnetic field have some similarities with those documented for the Laschamp excursion 41 kyr ago. Under the assumption that the dynamo processes for an eventual future reversal or excursion would be similar to those of the Laschamp excursion, we tentatively suggest that, whilst irreversible processes that will drive the geodynamo into a polarity change may have already started, a reversal or an excursion should not be expected before 500 to 1000 years.

  2. Effect of Cross-Correlation on Geomagnetic Forecast Accuracies

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

    2011-01-01

    Surface geomagnetic observation can determine up to degree L = 14 time-varying spherical harmonic coefficients of the poloidal magnetic field. Assimilation of these coefficients to numerical dynamo simulation could help us understand better the dynamical processes in the Earth's outer core, and to provide more accurate forecast of geomagnetic secular variations (SV). In our previous assimilation studies, only the poloidal magnetic field in the core is corrected by the observations in the analysis. Unobservable core state variables (the toroidal magnetic field and the core velocity field) are corrected via the dynamical equations of the geodynamo. Our assimilation experiments show that the assimilated core state converges near the CMB, implying that the dynamo state is strongly constrained by surface geomagnetic observations, and is pulled closer to the truth by the data. We are now carrying out an ensemble of assimilation runs with 1000 years of geomagnetic and archeo/paleo magnetic record. In these runs the cross correlation between the toroidal and the poloidal magnetic fields is incorporated into the analysis. This correlation is derived from the physical boundary conditions of the toroidal field at the core-mantle boundary (CMB). The assimilation results are then compared with those of the ensemble runs without the cross-correlation, aiming at understanding two fundamental issues: the effect of the crosscorrelation on (1) the convergence of the core state, and (2) the SV prediction accuracies. The constrained dynamo solutions will provide valuable insights on interpreting the observed SV, e.g. the near-equator magnetic flux patches, the core-mantle interactions, and possibly other geodynamic observables.

  3. Transport from chaotic orbits in the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Horton, W.; Tajima, T.

    1991-01-01

    The rapid change in direction and magnitude of the magnetic field vector in crossing the quasi-neutral sheet in the geomagnetic tail leads to deterministic Hamiltonian chaos. The finite correlation times in the single particle orbits due to the continuum of orbital frequencies leads to well-defined collisionless transport coefficients. The transport coefficients are derived for plasma trapped in the quasi-neutral sheet.

  4. Geomagnetic secular variation timescales under rapid rotation constraints

    NASA Astrophysics Data System (ADS)

    Coutelier, Maélie; Amit, Hagay; Christensen, Uli

    2016-04-01

    Based on geomagnetic observations, numerical dynamo simulations and frozen-flux theory it has been argued that the secular variation (SV) timescale of the magnetic field varies as 1l (where l is the spherical harmonic degree), except for the dipole. The equatorial symmetry of the core flow, which is expected due to rapid rotation effects, allows SV timescale decomposition into symmetric and asymmetric parts. We show in geomagnetic field models and in numerical dynamo simulations that the 1/l scaling law applies for the symmetric and asymmetric timescales as well separately. In both observed and simulated data the symmetric/asymmetric SV timescales are smaller/larger respectively, than in that of the full dataset. The symmetric dipole time scale is well fitted by the 1/l law in the geomagnetic field models, but not in the dynamo models. The opposite holds for the symmetric quadrupole time scales. Assuming that the dynamo models are more representative of the long-term behavior than the geomagnetic field models due to the much longer averaging time of the former, this may suggest that during the historical era the symmetric dipole SV timescale was exceptionally large and the symmetric quadrupole SV timescale was exceptionally small. Since present-day symmetric dipole SV timescale is below the 1/l fit, this may further suggest that the nearly constant dipole tilt between 1840-1960 was anomalous. Failure to explain the dipole SV timescales (both axial and equatorial) by the scaling law may suggest strong diffusion effects for the lowest degrees. Overall, our analytical fits for the symmetric and asymmetric SV timescales provide new insight into the re-organization times of different length scales in Earth's outer core.

  5. The geomagnetically trapped radiation environment: A radiological point of view

    NASA Technical Reports Server (NTRS)

    Holly, F. E.

    1972-01-01

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

  6. Spectral analysis of the multiple-altitude anomalous geomagnetic field

    NASA Astrophysics Data System (ADS)

    Tsvetkov, Yu. P.; Ivanov, V. V.; Petrov, V. G.; Filippov, S. V.; Brekhov, O. M.

    2016-11-01

    The spectra of the anomalous geomagnetic field measured at ground and balloon (30 km) altitudes were analyzed. The ground-based data were adapted from a map of the anomalous magnetic field of the Earth. A balloon surveys was carried out by the authors. It has been shown that the ground and balloon spectra of the anomalous magnetic field of the Earth substantially differ. Suppositions explaining the differences in the obtained spectra have been suggested.

  7. New evidence for geomagnetically trapped anomalous cosmic rays

    SciTech Connect

    Cummings, J.R.; Cummings, A.C.; Mewaldt, R.A.; Selesnick, R.S.; Stone, E.C. ); Rosenvinge, T.T. von )

    1993-09-15

    This article presents data from the SAMPEX satellite of trapped heavy ions in the ionosphere, with energies greater than 15 MeV/nucleon. The data shows trapped He, N, O, and Ne. These ions are thought to be of cosmic ray origin, and to have been trapped by the geomagnetic field due to the loss of electrons due to scattering events in the upper atmosphere.

  8. Types and Characteristics of Data for Geomagnetic Field Modeling

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  9. The effects of solar-geomagnetically induced currents on electrical systems in nuclear power stations

    SciTech Connect

    Subudhi, M.; Carroll, D.P.; Kasturi, S.

    1994-01-01

    This report presents the results of a study to evaluate the potential effects of geomagnetically induced currents (GICs) caused by the solar disturbances on the in-plant electrical distribution system and equipment in nuclear power stations. The plant-specific electrical distribution system for a typical nuclear plant is modeled using the ElectroMagnetic Transient Program (EMTP). The computer model simulates online equipment and loads from the station transformer in the switchyard of the power station to the safety-buses at 120 volts to which all electronic devices are connected for plant monitoring. The analytical model of the plant`s electrical distribution system is studied to identify the transient effects caused by the half-cycle saturation of the station transformers due to GIC. This study provides results of the voltage harmonics levels that have been noted at various electrical buses inside the plant. The emergency circuits appear to be more susceptible to high harmonics due to the normally light load conditions. In addition to steady-state analysis, this model was further analyzed simulating various plant transient conditions (e.g., loss of load or large motor start-up) occurring during GIC events. Detail models of the plant`s protective relaying system employed in bus transfer application were included in this model to study the effects of the harmonic distortion of the voltage input. Potential harmonic effects on the uniterruptable power system (UPS) are qualitatively discussed as well.

  10. Ionosphere data assimilation modeling of 2015 St. Patrick's Day geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Lin, C. H.; Matsuo, T.; Chen, W. H.

    2016-11-01

    The ionospheric plasma disturbances during a severe storm can affect human activities and systems, such as navigation and HF communication systems. Therefore, the forecast of ionospheric electron density is becoming an important topic recently. This study is conducted with the ionospheric assimilation model by assimilating the total electron content observations into the thermosphere-ionosphere coupling model with different high-latitude ionospheric convection models, Heelis and Weimer, and further to forecast the variations of ionospheric electron density during the 2015 St. Patrick's Day geomagnetic storm. The forecast capabilities of these two assimilation models are evaluated by the root-mean-square error values in different regions to discuss its latitudinal effects. Results show the better forecast in the electron density at the low-latitude region during the storm main phase and the recovery phase. The well reproduced eastward electric field at the low-latitude region by the assimilation model reveals that the electric fields may be an important factor to have the contributions on the accuracy of ionospheric forecast.

  11. Archaeomagnetic results from southern Italy and their bearing on geomagnetic secular variation

    NASA Astrophysics Data System (ADS)

    Evans, M. E.; Hoye, G. S.

    2005-07-01

    Archaeodirectional results from kilns and other baked structures in southern Italy are presented. They are generally compatible with the much larger data sets from France and Bulgaria. In particular, a summary of all the results associated with the well-known eruption of Vesuvius that destroyed Pompeii ( n = 9, D = 355°, I = 58°, α95 = 1.5°) provides a reliable archaeomagnetic anchor point supporting the French and Bulgarian master curves. It is extremely well-constrained in time and it comprises independent studies carried out in four different countries. Furthermore, it is derived from a diverse set of features agreement amongst which argues strongly against significant perturbations due to magnetic refraction, structural disturbance, or depositional shallowing. In terms of geomagnetic secular variation, we interpret the western European archaeomagnetic data summarized here in terms of an open loop caused by westward drift, followed by an inclination low spanning the first few centuries CE representing the signal of a static flux pulse that reaches a maximum magnetic moment of a few percent of the earth's main central dipole.

  12. Airglow-imaging observation of plasma bubble disappearance at geomagnetically conjugate points

    NASA Astrophysics Data System (ADS)

    Shiokawa, Kazuo; Otsuka, Yuichi; Lynn, Kenneth JW; Wilkinson, Philip; Tsugawa, Takuya

    2015-03-01

    We report the first observation of the disappearance of a plasma bubble over geomagnetically conjugate points. It was observed by airglow imagers at Darwin, Australia (magnetic latitude: -22°N) and Sata, Japan (21°N) on 8 August 2002. The plasma bubble was observed in 630-nm airglow images from 1530 (0030 LT) to 1800 UT (0300 LT) and disappeared equatorward at 1800 to 1900 UT (0300 to 0400 LT) in the field of view. The ionograms at Darwin and Yamagawa (20 km north of Sata) show strong spread-F signatures at approximately 16 to 21 UT. At Darwin, the F-layer virtual height suddenly increased from approximately 200 to approximately 260 km at the time of bubble disappearance. However, a similar F-layer height increase was not observed over the conjugate point at Yamagawa, indicating that this F-layer rise was caused not by an eastward electric field but by enhancement of the equatorward thermospheric wind over Darwin. We think that this enhancement of the equatorward neutral wind was caused by an equatorward-propagating large-scale traveling ionospheric disturbance, which was identified in the north-south keogram of 630-nm airglow images. We speculate that polarization electric field associated with this equatorward neutral wind drive plasma drift across the magnetic field line to cause the observed bubble disappearance.

  13. Generation of large-scale equatorial F-region plasma depletions during geomagnetic storms: A review

    NASA Astrophysics Data System (ADS)

    Sahai, Y.; Fagundes, P.; Bittencourt, J.; Pimenta, A.

    All-sky imaging observations of the F-region OI 630 nm nightglow emission allow us to visualize large - scale equatorial plasma depletions, generally known as transequatorial plasma bubbles. These quasi north south direction aligned- ionospheric plasma depletions are o tical signatures of strong range type equatorialp spread-F. An extensive data base of the OI 630 nm emission all-sky imaging- observations has been obtained at Cachoeira Paulista (22.7o S, 45.0 o W; dip latitude ~16o S), Brazil, between the years 1987 and 2000. An analysis of these observations revealed that normally large-scale ionospheric plasma depletions do not occur during the months of May to August (southern winter) in the Brazilian sector. However, large-scale ionospheric plasma depletions during thes e months have been observed on several occasions in association with geomagnetic storms. In this paper, a detailed analysis of the events when large - scale ionospheric plasma depletions were initiated and evolved during magnetic disturbances will be present ed and discussed.

  14. Temperature, density, and composition in the disturbed thermosphere from Esro 4 gas analyzer measurements - A global model

    NASA Technical Reports Server (NTRS)

    Jacchia, L. G.; Slowey, J. W.; Von Zahn, U.

    1977-01-01

    An analysis of density measurements of Ar, N2, O, and He made at 280 km with the gas analyzer aboard the polar-orbiting satellite Esro 4 has yielded a global model of the variations in temperature, density, and composition that occur in the disturbed thermosphere. In the model the increase of temperature over quiet conditions is a nonlinear function of the planetary geomagnetic index, its latitude profile being approximated by a fourth-power sin phi law, where phi is the 'invariant' magnetic latitude. A density wave proceeding from high latitudes is approximated by a fourth power cos phi law. A strong nonlinearity in the relation between the temperature variations and the variations in the height of the homopause explains a previously found behavioral difference in the variation of atomic oxygen during magnetic storms and during periods of sustained geomagnetic activity.

  15. Which Solar and Geomagnetic Drivers Control Earth's Upper Atmosphere Thermostat?

    NASA Astrophysics Data System (ADS)

    Knipp, D.; Mlynczak, M. G.; McGranaghan, R. M.; Kilcommons, L. M.

    2015-12-01

    Nitric Oxide (NO) is a trace component of Earth's upper atmosphere that allows Earth's thermosphere to cool in response to energy input from solar extreme ultraviolet (EUV) photons and geomagnetic activity. When created and excited, NO molecules provide a natural thermostat via infrared radiative emissions [Kockarts, 1980]. A record of this cooling over the last 13 years has been provided by Mlynczak et al. [2014]. Nitric Oxide emissions in concert with EUV photons, auroral particles, and neutral thermosphere circulation determine if geomagnetic storms will deliver a sudden powerful upheaval of Earth's upper atmosphere or a damped event. In this talk I will review recent findings about the forecastability of solar and magnetospheric control of this important thermospheric trace constituent. In particular, I will discuss the role of pseudo-streamers and helmet streamers in the solar wind, and the possible role of magnetic cloud orientation, in determining the extent of thermospheric NO storm response. Anticipating the thermospheric NO response to geomagnetic storms is a next step in improving satellite drag forecasting.

  16. Recent developments in the global geomagnetic observatory network

    NASA Astrophysics Data System (ADS)

    Chulliat, A.

    2011-12-01

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

  17. Geomagnetically Induced Currents and Impact on Power Grids

    NASA Astrophysics Data System (ADS)

    Pulkkinen, A. A.

    2015-12-01

    Geomagnetically induced currents (GIC) flowing in long manmade conductor systems have become one of the main space weather concerns. The potential for widespread problems in operating high-voltage power transmission systems during major geomagnetic storms has prompted increasing federal regulatory, science, industry and public interest in the problem. The impact caused by extreme storm events has been of special interest and consequently much of the recent GIC research has been focused on defining extreme GIC event scenarios and quantifying the corresponding transmission system response. In addition, there is an elevated need for developing next generation GIC prediction products for the power industry. In this presentation, I will discuss the key scientific concepts pertaining to GIC and provide a brief review of the recent progress in developing extreme storm scenarios and new predictive techniques. Much of the recent progress in understanding GIC and its impact on power grids has resulted from improved scientific community-power industry interactions. The common language and information exchange interfaces established between the two communities have led to significant progress in transitioning scientific knowledge into detailed impacts analyses. I will provide a few personal reflections on the interactions with the power industry. We also face a number of future challenges in specifying GIC, for example, in terms of more realistic modeling of the three-dimensional geomagnetic induction process. I will discuss briefly some of these future challenges.

  18. Why are intense geomagnetic storms so important for human life?

    NASA Astrophysics Data System (ADS)

    Saiz, E.; Cerrato, E.; Cid, C.; Aguado, J.

    2008-12-01

    Increasing knowledge concerning the space environment surrounding the earth has become one of the main focuses of research. This is mainly due to the fact that the adverse conditions in near-earth space cause significant damage to technological systems and, consequently, considerable economic losses. Many types of space weather-related anomalies and failings have been identified in recent years, thus converting adverse space weather into one of the threats facing modern human technology. Therefore important efforts should be made to find technical and operational solutions to space weather problems. In this framework, the need to implement reliable real-time warning tools is evident. Meanwhile, the fewer parameters involved in making predictions, the more valuable the tools will be. The present work develops a warning procedure based on the use of the z component of the interplanetary magnetic field only. The aim of this tool is to warn of the occurrence of intense geomagnetic variations, as measured by the geomagnetic Dst index. A comparison of our results with those criteria available in the relevant literature for the occurrence of intense geomagnetic activity shows a significant improvement in alerting capability.

  19. Geomagnetic Secular Variation Prediction with Thermal Heterogeneous Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Tangborn, Andrew; Jiang, Weiyuan

    2011-01-01

    It has long been conjectured that thermal heterogeneity at the core-mantle boundary (CMB) affects the geodynamo substantially. The observed two pairs of steady and strong magnetic flux lobes near the Polar Regions and the low secular variation in the Pacific over the past 400 years (and perhaps longer) are likely the consequences of this CMB thermal heterogeneity. There are several studies on the impact of the thermal heterogeneity with numerical geodynamo simulations. However, direct correlation between the numerical results and the observations is found very difficult, except qualitative comparisons of certain features in the radial component of the magnetic field at the CMB. This makes it difficult to assess accurately the impact of thermal heterogeneity on the geodynamo and the geomagnetic secular variation. We revisit this problem with our MoSST_DAS system in which geomagnetic data are assimilated with our geodynamo model to predict geomagnetic secular variations. In this study, we implement a heterogeneous heat flux across the CMB that is chosen based on the seismic tomography of the lowermost mantle. The amplitude of the heat flux (relative to the mean heat flux across the CMB) varies in the simulation. With these assimilation studies, we will examine the influences of the heterogeneity on the forecast accuracies, e.g. the accuracies as functions of the heterogeneity amplitude. With these, we could be able to assess the model errors to the true core state, and thus the thermal heterogeneity in geodynamo modeling.

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

    USGS Publications Warehouse

    Love, J.J.

    2011-01-01

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

  1. A global geomagnetic model based on historical and paleomagnetic data

    NASA Astrophysics Data System (ADS)

    Arneitz, P.; Leonhardt, R.; Fabian, K.

    2015-12-01

    Two main types of data are available to reconstruct the temporal and spatial geomagnetic field evolution. Historical instrumental measurements (direct data) extend from present day to the late Middle Age, and, prior the 19th century, consist mainly of declination values. Further back in the past, field reconstructions rely exclusively on the magnetization acquired by archaeological artefacts and rocks or sediments (indirect data). The major challenges for a reliable inversion approach are the inhomogeneous data distribution, the highly variable data quality, and inconsistent quality parameters. Available historical, archeomagnetic and volcanic records have been integrated into a single database together with corresponding metadata. This combination of compilations enables a joint evaluation of geomagnetic field records from different origins. In particular, data reliability and quality of indirect records are investigated using a detailed comparison with their direct counterparts. The collection forms the basis for combined inverse modeling of the geomagnetic field evolution. The iterative Bayesian inversion approach targets the implementation of reliable error treatments, which allow to combine data from different sources. Furthermore, a verification method scrutinizing the limitations of the applied inversion scheme and the used datasets is developed. Here, we will present strategies for the integration of different data types into the modeling procedure. The obtained modeling results and their validity will be discussed.

  2. Spurious behavior in volcanic records of geomagnetic field reversals

    NASA Astrophysics Data System (ADS)

    Carlut, Julie; Vella, Jerome; Valet, Jean-Pierre; Soler, Vicente; Legoff, Maxime

    2016-04-01

    Very large directional variations of magnetization have been reported in several lava flows recording a geomagnetic reversal. Such behavior could reflect real geomagnetic changes or be caused by artifacts due to post-emplacement alteration and/or non-ideal magnetic behavior. More recently, a high resolution paleomagnetic record from sediments pleads also for an extremely rapid reversal process during the last reversal. Assuming that the geomagnetic field would have moved by tens of degrees during cooling of moderate thickness lava flows implies brief episodes of rapid changes by a few degrees per day that are difficult to reconcile with the rate of liquid motions at the core surface. Systematical mineralogical bias is a most likely explanation to promote such behavior as recently reconsidered by Coe et al., 2014 for the rapid field changes recorded at Steens Mountain. We resampled three lava flows at La Palma island (Canarias) that are sandwiched between reverse polarity and normal polarity flows associated with the last reversal. The results show an evolution of the magnetization direction from top to bottom. Thermal demagnetization experiments were conducted using different heating and cooling rates. Similarly, continuous demagnetization and measurements. In both cases, we did not notice any remagnetization associated with mineralogical transformations during the experiments. Magnetic grain sizes do not show any correlation with the amplitude of the deviations. Microscopic observations indicate poor exsolution, which could suggests post-cooling thermochemical remagnetization processes.

  3. Holocene Geomagnetic Change in the Northern North Atlantic

    NASA Astrophysics Data System (ADS)

    Stoner, J. S.; Channell, J. E.; Mazaud, A.; Xuan, C.; Strano, S. E.; Olafsdottir, S.; Jennings, A. E.

    2012-12-01

    High-resolution and well-dated paleomagnetic records constrain the geomagnetism of the Holocene North Atlantic. These records comprise ultra-high resolution sediment records from lakes (Haukadalsvatn, Iceland) and from continental margins (MD99-2269, N Iceland shelf; MD99-2322, E. Greenland), and from high accumulating (>50 cm/kyr) deep-sea sediments from the Eirik Drift, Labrador Sea (IODP Site U1305). Similarities among these directional paleomagnetic secular variation (PSV) records from very different environments imply that the records provide robust reconstructions of the paleo-geomagnetic field. Assuming that the age of magnetization is best defined by PSV in the highest sedimentation rate (>200 cm /kyr) records, allows us to place northern North Atlantic PSV and relative paleointensity (RPI) into a regional context. Northern North Atlantic PSV and RPI are more consistent with European than North American records, and the evolution of virtual geomagnetic poles (VGP) are temporally and longitudinally similar too global reconstructions, though with much larger latitudinal variations. The largest deviation from a geocentric axial dipole, in contrast to the usual assumption, is observed during times of highest field intensities in the North Atlantic and globally, while the highest rates of VGP change are associated with North Atlantic field intensity lows. These observations are consistent with the hypothesis that PSV results from temporal oscillations of flux concentrations (lobes) at a few recurrent locations.

  4. Midlatitude cooling caused by geomagnetic field minimum during polarity reversal

    PubMed Central

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

    2013-01-01

    The climatic effects of cloud formation induced by galactic cosmic rays (CRs) has recently become a topic of much discussion. The 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

  5. Hf Radio Propagation At High Latitudes: Observations and Predictions For Quiet and Disturbed Conditions

    NASA Astrophysics Data System (ADS)

    Jacobsen, B.; Jodalen, V.; Cannon, P. S.; Smith, O.; Angling, M. J.

    High-frequency (HF) radio communications at high latitudes are greatly affected by geomagnetic and ionospheric conditions, and both civilian and military users need re- liable forecasts of the propagation environment. In recent years, a network of channel sounders known as DAMSON (Doppler and multipath sounding network) has been operated in Scandinavia (including Svalbard) on a nearly continous basis. We have analysed DAMSON measurements of multipath spread, Doppler shift and spread, and signal-to-noise ratio on four HF paths under both quiet and disturbed geomagnetic conditions. Correlations have been made with data from other ground-based installa- tions in the same geographic region (HF radars, magnetometers, ionosondes). Long signal delays (several ms) are regularly observed during midday at frequencies above the predicted Maximum Usable Frequency (MUF) and could possibly be caused by ground scatter. Large Doppler spreads (tens of Hz) are observed during disturbed con- ditions (substorms), when the ionospheric reflection point is located within the auroral oval. We suggest that forecasts of the HF multipath and Doppler environment based on sounder measurements could be utilized as additions to the regular HF predictions of e.g., the MUF and LUF of a propagation path.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  7. Supplemental Summary of Cutoff Rigidities Calculated Using the International Geomagnetic Reference Field for Various Epochs.

    DTIC Science & Technology

    1982-11-01

    Rigidities Calculated Using the International -Geomagnetic Reference Field for Various Epochs M.A. SHEA D.F. SMART 1 NOVEMBER 1982 Approved for publie...SUMMARY OF CUTOFF Scientific. Interim. RIGIDITIES CALCULATED USING THE INTER -_ _________ NATIONAL GEOMAGNETIC REFERENCE FIELD 6 PERFORMING 01G. REPORT...n-b.’I Cosmic rays Cutoff rigidities Geomagnetic field 20 ABSTRACT (ContinuC0 e o, sid. it ---. 0, -,d id- 5,.- 550,5- Tables of cosmic-ray cutoff

  8. Biotropic geomagnetic pulsations Pc1 resulting from the magnetic storm of March 17, 2015

    NASA Astrophysics Data System (ADS)

    Slivinsky, A. P.

    2016-12-01

    Data obtained by a Hall sensor-based magnetic field detector have been used to record the spectral components of the geomagnetic field. An analysis of specific features of the spectral characteristics of geomagnetic fluctuations has indicated that the pulsations identified in the vicinity of the strong magnetic storm of March 17, 2015, are "pearl"-type fluctuations, i.e., biotropic geomagnetic Pc1 pulsations.

  9. A database of synthetic observations for geomagnetic data assimilation practice

    NASA Astrophysics Data System (ADS)

    Fournier, A.; Aubert, J.; Thebault, E.; Schaeffer, N.

    2012-04-01

    Data assimilation aims at producing an optimal estimate of the state of the dynamical system one is interested in by combining two sources of information : physical laws (in the form of a numerical model) and observations. A mandatory step during the development of a data assimilation framework involves a validation phase using synthetic data. In this well-controlled environment, the true dynamical trajectory of the system is known (it results from the integration of the numerical model), and it is used to generate synthetic observations. Those are subsequently used to assess the efficacy, and to highlight possible shortcomings, of the chosen methodology. Data assimilation has recently come to the fore in geomagnetism (e.g. Fournier et al., 2010), a surge motivated by our increased ability to observe the geomagnetic field (thanks to dedicated satellite missions), and by the concurrent progress in the numerical description of core dynamics. Open questions are related to the type of physical models one should resort to, and to the choice of a suitable algorithm, able to integrate the highly heterogeneous geomagnetic record at our disposal, and to deal with the non-linearities of the problem at hand (e.g. Aubert & Fournier, 2011; Fournier et al., 2011). Here we report on the construction of a database of synthetic observations meant at reproducing the heterogeneity of the geomagnetic record (in terms of temporal and spatial coverage). This database relies on two dynamical trajectories: a long-term dynamical trajectory (spanning the equivalent of the past few millenia) computed from a three-dimensional, convection-driven, dynamo model, able to represent accurately the long-term variability of the geomagnetic field a short-term dynamical trajectory (spanning the equivalent of a few decades), computed from a high-resolution three-dimensional model, able to represent interannual to decadal core processes (e.g. Gillet et al., 2011), and whose basic state is determined from

  10. Effects of magnetic fields produced by simulated and real geomagnetic storms on rats

    NASA Astrophysics Data System (ADS)

    Martínez-Bretón, J. L.; Mendoza, B.

    2016-03-01

    In this paper we report experiments of arterial pressure (AP) measurements of ten Wistar rats subjected to geomagnetic field changes and to artificially stimulated magnetic field variations. Environmental electromagnetic effects were screened using a semianechoic chamber, which allowed us to discern the effects associated with geomagnetic storms. We stimulated the subjects with a linear magnetic profile constructed from the average changes of sudden storm commencement (SSC) and principal phases of geomagnetic storms measured between 1996 and 2008 with Dst ⩽ -100 nT. Although we found no statistically significant AP variations, statistically significant AP changes were found when a geomagnetic storm occurred during the experimental period. Using the observed geomagnetic storm variations to construct a geomagnetic profile to stimulate the rats, we found that the geomagnetic field variations associated to the SSC day were capable of increasing the subjects AP between 7% and 9% from the reference value. Under this magnetic variation, the subjects presented a notably restless behavior not seen under other conditions. We conclude that even very small changes in the geomagnetic field associated with a geomagnetic storm can produce a measurable and reproducible physiological response.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Dyment, J.; Arkani-Hamed, J.

    2005-12-01

    Since the classic paper of Vine and Matthews (Nature, 1963), marine magnetic anomalies are commonly used to date the ocean floor through comparison with the geomagnetic polarity time scale and proper identification of reversal sequences. As a consequence, the classical model of rectangular prisms bearing a normal / reversed magnetization has been dominant in the literature for more than 40 years. Although the model explains major characteristics of the sea-surface magnetic anomalies, it is contradicted by (1) recent advances on the geophysical and petrologic structure of the slow-spreading oceanic crust, and (2) the observation of short-term geomagnetic time variations, both of which are more complex than assumed in the classical model. Marine magnetic anomalies may also provide information on the magnetization of the oceanic crust as well as short-term temporal fluctuations of the geomagnetic field. The "anomalous skewness", a residual phase once the anomalies have been reduced to the pole, has been interpreted either in terms of geomagnetic field variations or crustal structure. The spreading-rate dependence of anomalous skewness rules out the geomagnetic hypothesis and supports a spreading-rate dependent magnetic structure of the oceanic crust, with a basaltic layer accounting for most of the anomalies at fast spreading rates and an increasing contribution of the deeper layers with decreasing spreading rate. The slow cooling of the lower crust and uppermost mantle and serpentinization, a low temperature alteration process which produces magnetite, are the likely cause of this contribution, also required to account for satellite magnetic anomalies over oceanic areas. Moreover, the "hook shape" of some sea-surface anomalies favors a time lag in the magnetization acquisition processes between upper and lower magnetic layers: extrusive basalt acquires a thermoremanent magnetization as soon as emplaced, whereas the underlying peridotite and olivine gabbro cool slowly

  13. Disturbance regime and disturbance interactions in Rocky Mountain subalpine forest

    USGS Publications Warehouse

    Veblen, Thomas T.; Hadley, Keith S.; Nel, Elizabeth M.; Kitzberger, Thomas; Reid, Marion; Villalba, Ricardo

    1994-01-01

    1 The spatial and temporal patterns of fire, snow avalanches and spruce beetle out-breaks were investigated in Marvine Lakes Valley in the Colorado Rocky Mountains in forests of Picea engelmannii, Abies lasiocarpa, Pseudotsuga menziesiiand Populus tremuloides. Dates and locations of disturbances were determined by dendrochronological techniques. A geographic information system (GIS) was used to calculate areas affected by the different disturbance agents and to examine the spatial relationships of the different disturbances. 2 In the Marvine Lakes Valley, major disturbance was caused by fire in the 1470s, the 1630s and the 1870s and by spruce beetle outbreak in c. 1716, 1827 and 1949. 3 Since c. 1633, 9% of the Marvine Lakes Valley has been affected by snow avalanches, 38.6% by spruce beetle outbreak and 59.1% by fire. At sites susceptible to avalanches, avalanches occur at a near-annual frequency. The mean return intervals for fire and spruce beetle outbreaks are 202 and 116.5 years, respectively. Turnover times for fire and spruce beetle outbreaks are 521 and 259 years, respectively. 4 Several types of disturbance interaction were identified. For example, large and severe snow avalanches influence the spread of fire. Similarly, following a stand-devastating fire or avalanche, Picea populations will not support a spruce beetle outbreak until individual trees reach a minimum diameter which represents at least 70 years' growth. Thus, recent fires and beetle outbreaks have nonoverlapping distributions.

  14. Physics of natural and hf-induced ionospheric disturbances and their effects on radio communication. Final report, 1 February 1983-30 June 1985

    SciTech Connect

    Not Available

    1985-06-30

    A theoretical study is reported of ionospheric disturbances caused by either natural or man-made processes. Thirteen papers published in either technical journals or conference proceedings are compiled in this report. These papers discuss (1) the identification of the sources of free energy, the optimum conditions for plasma instabilities as the courses of naturally occurring ionospheric irregularities, and (2) the nonlinear effects leading to the h-f ionospheric disturbances such as lower-hybrid waves, upper-hybrid waves, ionospheric irregularities, and geomagnetic field fluctuations.

  15. Investigation of traveling ionospheric disturbances

    NASA Technical Reports Server (NTRS)

    Grossi, M.; Estes, R. D.

    1981-01-01

    Maximum entropy power spectra of the ionospheric electron density were constructed to enable PINY to compare them with the power independently obtained by PINY with in situ measurements of ionospheric electron density and neutral species performed with instrumentation carried by the Atmospheric Explorer (AE) satellite. This comparison corroborated evidence on the geophysical reality of the alleged electron density irregularities detected by the ASTP dual frequency Doppler link. Roughly half of the localized wave structures which are confined to dimensions of 1800 km or less (as seen by an orbiting Doppler baseline) were found to be associated with the larger crest of the geomagnetic anomaly in the Southern (winter) Hemisphere in the morning. The observed nighttime structures are also associated with local peaks in the electron density.

  16. Two-Step Forecast of Geomagnetic Storm Using Coronal Mass Ejection and Solar Wind Condition

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz = -5 nT or Ey = 3 mV/m for t = 2 h for moderate storms with minimum Dst less than -50 nT) (i.e. Magnetic Field Magnitude, B (sub z) less than or equal to -5 nanoTeslas or duskward Electrical Field, E (sub y) greater than or equal to 3 millivolts per meter for time greater than or equal to 2 hours for moderate storms with Minimum Disturbance Storm Time, Dst less than -50 nanoTeslas) and a Dst model developed by Temerin and Li (2002, 2006) (TL [i.e. Temerin Li] model). Using 55 CME-Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90 percent) than the forecasts based on the TL model (87 percent). However, the latter produces better forecasts for 24 nonstorm events (88 percent), while the former correctly forecasts only 71 percent of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80 percent) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (n, i.e. cap operator - the intersection set that is comprised of all the elements that are common to both), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81 percent) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (?, i.e. cup operator - the union set that is comprised of all the elements of either or both

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The

  18. MoSST DAS: The First Working Geomagnetic Data Assimilation System

    NASA Technical Reports Server (NTRS)

    Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

    2011-01-01

    The Earth possesses an internal magnetic field (geomagnetic field) generated by convection in the outer core (geodynamo). Previous efforts have been focused along two distinct paths: (1) numerical geodynamo modeling to understand the origin of the geomagnetic field, and the mechanisms of geomagnetic secular variations (SV); and (2) geomagnetic field modeling to map the spatial/temporal variations of the field from geomagnetic data, and to derive core properties, e.g. inversion