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Sample records for geomagnetically quiet conditions

  1. Statistical Characteristics of EMIC Waves Observed at Geosynchronous Orbit during Quiet Geomagnetic Conditions

    NASA Astrophysics Data System (ADS)

    Park, J. S.; Kim, K. H.; Lee, D. H.; Lee, E.; Jin, H.

    2014-12-01

    It is generally accepted that the electromagnetic ion cyclotron (EMIC) waves can be generated under the conditions of anisotropic (T⊥ > T∥) and energetic (larger than a few tens keV) ion population. Such conditions are expected when the magnetospheric convection is enhanced or when the magnetosphere is compressed by solar wind dynamic pressure enhancement. Even in the absence of strong magnetospheric convection or strong solar wind dynamic pressure enhancements, we have observed EMIC waves at geosynchronous orbit. In this study, we report the GOES observations of the EMIC waves excited during quiet geomagnetic conditions (Kp ≤ 1) in the period from January 2007 to December in 2008. Unlike previous studies, the occurrence rate of quiet time EMIC waves is dominant in morning-to-afternoon sector. We will examine the source of free energy to excite quiet time EMIC waves and also examine wave's characteristics.

  2. Low-latitude Pi2 pulsations during intervals of quiet geomagnetic conditions (Kp≤1)

    NASA Astrophysics Data System (ADS)

    Kwon, H.-J.; Kim, K.-H.; Jun, C.-W.; Takahashi, K.; Lee, D.-H.; Lee, E.; Jin, H.; Seon, J.; Park, Y.-D.; Hwang, J.

    2013-10-01

    It has been reported that Pi2 pulsations can be excited under extremely quiet geomagnetic conditions (Kp=0). However, there have been few comprehensive reports of Pi2 pulsations in such a near ground state magnetosphere. To understand the characteristics of quiet-time Pi2 pulsations, we statistically examined Pi2 events observed on the nightside between 1800 and 0600 local time at the low-latitude Bohyun (BOH, L = 1.35) station in South Korea. We chose year 2008 for analysis because geomagnetic activity was unusually low in that year. A total of 982 Pi2 events were identified when Kp≤1. About 80% of the Pi2 pulsations had a period between 110 and 300 s, which significantly differs from the conventional Pi2 period from 40 to 150 s. Comparing Pi2 periods and solar wind conditions, we found that Pi2 periods decrease with increasing solar wind speed, consistent with the result of Troitskaya (1967). The observed wave properties are discussed in terms of plasmaspheric resonance, which has been proposed for Pi2 pulsations in the inner magnetosphere. We also found that Pi2 pulsations occur quasi-periodically with a repetition period of ˜23-38 min. We will discuss what determines such a recurrence time of Pi2 pulsations under quiet geomagnetic conditions.

  3. Magnetic Field Perturbations from Currents in the Dark Polar Regions During Quiet Geomagnetic Conditions

    NASA Astrophysics Data System (ADS)

    Friis-Christensen, E.; Finlay, C. C.; Hesse, M.; Laundal, K. M.

    2017-02-01

    In the day-side sunlit polar ionosphere the varying and IMF dependent convection creates strong ionospheric currents even during quiet geomagnetic conditions. Observations during such times are often excluded when using satellite data to model the internal geomagnetic main field. Observations from the night-side or local winter during quiet conditions are, however, also influenced by variations in the IMF. In this paper we briefly review the large scale features of the ionospheric currents in the polar regions with emphasis on the current distribution during undisturbed conditions. We examine the distribution of scalar measurements of the magnetic field intensity minus predictions from a geomagnetic field model. These `residuals' fall into two main categories. One category is consistently distributed according to the well-known ionospheric plasma convection and its associated Birkeland currents. The other category represent contributions caused by geomagnetic activity related to the substorm current wedge around local magnetic midnight. A new observation is a strong IMF By control of the residuals in the midnight sector indicating larger ionospheric currents in the substorm current wedge in the northern polar region for By > 0 and correspondingly in the southern hemisphere for By < 0.

  4. Magnetic Field Perturbations from Currents in the Dark Polar Regions During Quiet Geomagnetic Conditions

    NASA Astrophysics Data System (ADS)

    Friis-Christensen, E.; Finlay, C. C.; Hesse, M.; Laundal, K. M.

    2017-03-01

    In the day-side sunlit polar ionosphere the varying and IMF dependent convection creates strong ionospheric currents even during quiet geomagnetic conditions. Observations during such times are often excluded when using satellite data to model the internal geomagnetic main field. Observations from the night-side or local winter during quiet conditions are, however, also influenced by variations in the IMF. In this paper we briefly review the large scale features of the ionospheric currents in the polar regions with emphasis on the current distribution during undisturbed conditions. We examine the distribution of scalar measurements of the magnetic field intensity minus predictions from a geomagnetic field model. These `residuals' fall into two main categories. One category is consistently distributed according to the well-known ionospheric plasma convection and its associated Birkeland currents. The other category represent contributions caused by geomagnetic activity related to the substorm current wedge around local magnetic midnight. A new observation is a strong IMF By control of the residuals in the midnight sector indicating larger ionospheric currents in the substorm current wedge in the northern polar region for By > 0 and correspondingly in the southern hemisphere for By < 0.

  5. A Statistical Study of EMIC Waves Observed at THEMIS Probes in the Outer (L > 7) Magnetosphere Under Quiet Geomagnetic Conditions

    NASA Astrophysics Data System (ADS)

    Kim, G. J.; Kim, K. H.; Park, J. S.; Lee, E.; Lee, D. H.

    2014-12-01

    Electromagnetic ion cyclotron (EMIC) waves can be generated in the equatorial magnetosphere by an anisotropic temperature distribution (T⊥>T∥) of energetic (10-100 keV) ions. They are typically observed in the afternoon sector with a wide L range (L > 7) and occur near the plasmapause. Thus, it has been suggested that the distribution of EMIC wave occurrence in the afternoon sector is associated with the plasmaspheric expansion (i.e., plasmapsheric bulge or plume). Since the plasmapause is further away the earth during times of low geomagnetic activity, it is expected that EMIC wave's spatial distribution under quiet geomagnetic conditions could be different from that under averaged geomagnetic conditions. In our study we investigate the spatial distribution of EMIC waves during quiet geomagnetic conditions (Kp ≤ 1) in the outer magnetosphere (L > 7) using the magnetic field data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft from 2008 to 2009. We also examine the spatial distribution of cold plasma density estimated from THEMIS spacecraft potential data and compare it with EMIC wave occurrence during quiet geomagnetic conditions.

  6. Earthquake aftereffects in the Equatorial Ionization Anomaly region under geomagnetic quiet and storm conditions

    NASA Astrophysics Data System (ADS)

    Gulyaeva, T. L.; Arikan, F.; Stanislawska, I.

    2017-07-01

    In addition to multi-scale spatio-temporal trends that shape the ionosphere variability, the ionosphere responds to the disturbances that are solar, geomagnetic and seismic in origin. In this study, post-seismic ionospheric disturbances are investigated retrospectively from 1999 to 2015 using two different sets of ionospheric maps of the F2 layer critical frequency, foF2. One set of foF2 maps is obtained by assimilating Global Ionospheric Maps (GIM) of Total Electron Content (TEC) into IRI-Plas model (IRI-Plas-foF2). Another set of hourly foF2 maps is obtained using PRIME-251 mapping technique (PRIME-foF2) by the assimilation of ionosonde foF2 data into IRI-CCIR model. The geomagnetic storms affecting the ionosphere are determined with relevant thresholds of geomagnetic AE, aa, ap, ap(τ) and Dst indices. It is observed that more than 60% of the earthquakes occur in the Equatorial Ionization Anomaly (EIA) region within the belt of geomagnetic latitudes ±40° N and geographic longitudes 90-190° E. The co-seismic foF2 disturbances, DfoF2, are identified for the cells of the map if an instant foF2 value is outside of pre-defined bounds of foF2 median (μ) and standard deviation (σ), μ ± 1σ, in the map fragment of 1000 km radius around the earthquake hypocenter. The results of positive ionospheric disturbances, DfoF2p, and negative disturbances, DfoF2n, in the EIA region during the 12 h after earthquake differ with respect to geomagnetic quiet and storm conditions, nighttime and daytime, magnitude and depth of the earthquake. The maximum spatial variability (for more than 50% of map cells in the vicinity of hypocenter) is observed with positive disturbances (DfoF2p) for the earthquakes that occurred during daytime at a depth of 70-300 km.

  7. Global empirical model of critical frequency of the ionospheric F2-layer for quiet geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Shubin, V. N.

    2017-07-01

    Using the foF2 database obtained from satellites and ground-based ionospheric stations, we have constructed a global empirical model of the critical frequency of the ionospheric F2-layer (SDMF2—Satellite and Digisonde Data Model of the F2 layer) for quiet geomagnetic conditions ( Kp < 3). The input parameters of this model are the geographical coordinates, UT, day, month, year, and the integral index F10.7 ( day, τ = 0.96) of solar activity for a given day. The SDMF2 model was based on the Legendre method for the spatial expansion of foF2 monthly medians to 12 in latitude and 8 in longitude of spherical harmonics. The resulting spatial coefficients have been expanded by the Fourier method in three spherical harmonics with respect to UT. The effect of the saturation of critical frequency of the ionospheric F2-layer at high solar activity was described in the SDMF2 model by foF2 as a logarithmic function of F10.7 ( day, τ = 0.96). The difference between the SDMF2 and IRI models is a maximum at low solar activity as well as in the Southern Hemisphere and in the oceans. The testing on the basis of ground-based and satellite data has indicated that the SDMF2 model is more accurate than the IRI model.

  8. Formation mechanisms of the midlatitudinal NmF2 semiannual anomaly under daytime quiet geomagnetic conditions at low solar activity

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

    The F-region peak electron densities NmF2 measured during daytime quiet geomagnetic conditions at low solar activity on January 22, 2008, April 8, 1997, July 12, 1986, and October 26, 1995, are compared. Ionospheric parameters are measured by the ionosonde and incoherent scatter radar at Millstone Hill and calculated with the use of a 1D nonstationary ionosphere-plasmasphere model of number densities and temperatures of electrons and ions at middle geomagnetic latitudes. The formation of the semiannual anomaly of the midlatitudinal NmF2 under daytime quiet geomagnetic conditions at low solar activity is studied. The study shows that the semiannual NmF2 anomaly occurs due to the total impact of three main causes: seasonal variations in the velocity of plasma drift along the geomagnetic field due to the corresponding variations in the components of the neutral wind velocity; seasonal variations in the composition and temperature of the neutral atmosphere; and the dependence of the solar zenith angle on a number of the day in the year at the same solar local time.

  9. 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.

  10. Pi2 Pulsations During Extremely Quiet Geomagnetic Condition: Van Allen Probe Observations

    NASA Astrophysics Data System (ADS)

    Ghamry, Essam

    2017-06-01

    A ultra low frequency (ULF) wave, Pi2, has been reported to occur during periods of extremely quiet magnetospheric and solar wind conditions. And no statistical study on the Pi2 has been performed during extremely quiet conditions, using satellite observations to the author’s knowledge. Also Pi2 pulsations in the space fluxgate magnetometers near perigee failed to attract scientist’s attention previously. In this paper, Pi2 pulsations detected by the Van Allen probe satellites (VAP-A & VAP-B) were investigated statistically. During the period from October 2012 to December 2014, ninety six Pi2 events were identified using VAP when Kp = 0 while using Kakioka (KAK, L = 1.23) as a reference ground station. Seventy five events had high coherence between VAP-Bz and H components at KAK station. As a result, it was found that 77 % of the events had power spectra between 5 and 12 mHz, which differs from the regular Pi2 band range of from 6.7 to 25 mHz. In addition, it was shown that it is possible to observe Pi2 pulsations from space fluxgate magnetometers near perigee. Twenty two clean Pi2 pulsations were found where L < 4 and four examples of Pi2 oscillations at different L shells are presented in this paper.

  11. 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.

  12. Regional TEC model under quiet geomagnetic conditions and low-to-moderate solar activity based on CODE GIMs

    NASA Astrophysics Data System (ADS)

    Feng, Jiandi; Jiang, Weiping; Wang, Zhengtao; Zhao, Zhenzhen; Nie, Linjuan

    2017-08-01

    Global empirical total electron content (TEC) models based on TEC maps effectively describe the average behavior of the ionosphere. However, the accuracy of these global models for a certain region may not be ideal. Due to the number and distribution of the International GNSS Service (IGS) stations, the accuracy of TEC maps is geographically different. The modeling database derived from the global TEC maps with different accuracy is likely one of the main reasons that limits the accuracy of the new models. Moreover, many anomalies in the ionosphere are geographic or geomagnetic dependent, and as such the accuracy of global models can deteriorate if these anomalies are not fully incorporated into the modeling approach. For regional models built in small areas, these influences on modeling are immensely weakened. Thus, the regional TEC models may better reflect the temporal and spatial variations of TEC. In our previous work (Feng et al., 2016), a regional TEC model TECM-NEC is proposed for northeast China. However, this model is only directed against the typical region of Mid-latitude Summer Nighttime Anomaly (MSNA) occurrence, which is meaningless in other regions without MSNA. Following the technique of TECM-NEC model, this study proposes another regional empirical TEC model for other regions in mid-latitudes. Taking a small area BeiJing-TianJin-Tangshan (JJT) region (37.5°-42.5° N, 115°-120° E) in China as an example, a regional empirical TEC model (TECM-JJT) is proposed using the TEC grid data from January 1, 1999 to June 30, 2015 provided by the Center for Orbit Determination in Europe (CODE) under quiet geomagnetic conditions. The TECM-JJT model fits the input CODE TEC data with a bias of 0.11TECU and a root mean square error of 3.26TECU. Result shows that the regional model TECM-JJT is consistent with CODE TEC data and GPS-TEC data.

  13. Variability of the F region of the equatorial ionosphere during quiet geomagnetic conditions prior to strong earthquakes

    NASA Astrophysics Data System (ADS)

    Depueva, A. Kh.

    2014-01-01

    The deviations in the hourly values of the F-region critical frequency from the monthly median for the ionospheric Huancayo station located near the magnetic equator during periods of quiet geomagnetic conditions are analyzed for 1957-1987. Ionospheric data for five days prior, one day after, and directly for the days of 33 strong (with a magnitude M ≥ 5.5) earthquakes with epicenters in the American longitudinal sector were used. It is revealed that, in 24 cases 1-5 days prior to the considered earthquakes, a decrease in the critical frequencies by more than 20% with a duration from one to six hours was observed mainly in the nighttime. One can assume that these effects (at least, part of them) are related to the processes of earthquake preparation. Disturbances were mainly detected in cases when the radius of the earthquake preparation zone exceeded the distance between the epicenter and the observation station. The need for a further study of the characteristics of different kinds of coupling "from below" on electrodynamical processes in the low-latitude ionosphere for successful recognition of disturbances of the seismogenic nature is noted.

  14. 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

    Twelve empirical local models have been developed for the long-term prediction of the ionospheric characteristic M3000F2, and then used as starting point for the development of a short-term forecasting empirical regional model of M3000F2 under not quiet geomagnetic conditions. Under the assumption that the monthly median measurements of M3000F2 are linearly correlated to the solar activity, a set of regression coefficients were calculated over 12 months and 24 h for each of 12 ionospheric observatories located in the European area, and then used for the long-term prediction of M3000F2 at each station under consideration. Based on the 12 long-term prediction empirical local models of M3000F2, 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, which are able to provide short-term forecasts of the critical frequency of the F2 layer (foF2STF) up to three hours in advance, it was possible to considerer the Brudley-Dudeney algorithm as a function of foF2STF to correct RM_M3000F2 and thus obtain 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 the case of moderate geomagnetic activity, the Bradley-Dudeney correction factor does not

  15. Dependences of statistical characteristics of NmE on the month of the year at middle and low latitudes under daytime geomagnetically quiet conditions at low solar activity

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    Month-to-month changes in the statistical characteristics of the ionospheric E layer peak electron density NmE at medium and low geomagnetic latitudes under daytime geomagnetically quiet conditions are investigated. Critical frequencies of the ionospheric E layer measured by the middle latitude ionosonde Boulder and low latitude ionosondes Huancayo and Jicamarca at low solar activity from 1957 to 2015 have been used in the conducted statistical analysis. The mathematical expectation of NmE, standard deviation of NmE from the expectation of NmE, and NmE variation coefficient have been calculated for each month of the year. The months of the formation of extrema of these statistical parameters of NmE were found.

  16. PENGUIn/AGO and THEMIS conjugate observations of whistler mode chorus waves in the dayside uniform zone under steady solar wind and quiet geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Keika, Kunihiro; Spasojevic, Maria; Li, Wen; Bortnik, Jacob; Miyoshi, Yoshizumi; Angelopoulos, Vassilis

    2012-07-01

    We perform a case study of conjugate observations of whistler mode chorus waves on the dayside made on 26 July 2008 by three THEMIS spacecraft and ground-based ELF/VLF receivers at the Automatic Geophysical Observatories (AGO) in Antarctica supported by the U.S. Polar Experiment Network for Geospace Upper-atmosphere Investigations (PENGUIn) project. The dayside chorus waves were excited during a period of no substorm activity with geomagnetic indices indicating quiet conditions (Dst ˜ -10 nT; AE < 200 nT). The solar wind dynamic pressure was almost constant during the chorus wave intensification. Conjugate observations in the outer magnetosphere confirm that the chorus intensification was localized within the radial distance R = 7-10 RE near noon (12.5 < MLT < 13.5 h). The waves persisted for at least 1.5 h in the same location, where field lines are not accompanied by off-equatorial minimum-B pockets but rather exhibit nearly zero dB/ds, the field-aligned gradient in B-magnitude, over a wide range of magnetic latitudes (˜±20°). The location did not seem to corotate with the Earth or drift with the energetic electrons. The chorus waves consisted of discrete, rising tone elements, propagating away from the magnetic equator, quasi-parallel to the ambient magnetic field (wave-normal angles < 20°). We conclude that the long-lasting, localized, quiet time dayside chorus amplification was due to the nearly zero dB/ds conditions that occur naturally in the dayside uniform zone (DUZ), the transition region between the near-Earth dipole and the compressed, off-equatorial double-minimum field configuration found closer to the magnetopause. We thus suggest that the magnetic field configuration in the dayside outer magnetosphere plays a key role in the generation of dayside chorus waves under quiet geomagnetic conditions.

  17. 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

  18. On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Liu, Libo; Zhao, Biqiang; Lei, Jiuhou; Wan, Weixing

    2011-12-01

    The equatorial mass anomaly (EMA) in the thermosphere and equatorial ionization anomaly (EIA) in the ionosphere are two interesting phenomena in low-equatorial latitude regions. Previous studies have shown that the EMA appears between 1000 and 2000 local time (LT) and its location of trough is aligned with dip equator, indicating the plausible role of the EIA structure in the development of EMA. In this report, we conducted a statistical study of the occurrence of postmidnight EMA and EIA on the basis of the CHAMP in situ measurements during 2002-2008. Our results revealed that clear EMA and EIA structures are sometimes visible in the postmidnight sector (0100-0600 LT) during geomagnetic quiet periods (Kp < 3). The postmidnight EMA is not necessarily accompanied by the EIA signature in both case study and statistics sense being distinct from the daytime situation. In addition, the occurrence rates of postmidnight EMA and EIA display contrasting behavior with respect to their local time, longitudinal and solar activity dependences. The highest occurrence rate for EMA is 8% at around 0300 LT, while the occurrence rate of the EIA decreases gradually from about 30% at around 2300 LT to ˜5% at 0600 LT. Longitudinal occurrence of postmidnight EIA presents a wave-like pattern; however, no salient feature appears for the longitudinal occurrence of EMA. Postmidnight EMA is more likely to occur at lower solar activity, whereas an opposite trend presents in the EIA. On the basis of above results, our findings imply that a simple EIA-EMA cause-effect relationship does not hold in the postmidnight sector.

  19. Long-term monthly statistics of mid-latitudinal NmF2 in the Northern geographic hemisphere during geomagnetically quiet and steadily low solar activity conditions

    NASA Astrophysics Data System (ADS)

    Pavlov, Anatoli; Pavlova, Nadezhda

    2016-07-01

    Long-term mid-latitude hourly values of NmF2 measured in 1957-2015 by 10 ionosondes (Point Arguello, Wallops Is., Boulder, de l'Ebre, Rome, Ottawa, Pruhonice, Dourbes, Slough, and Juliusruh) in the Northern geographic hemisphere were processed to select periods of geomagnetically quiet and low solar activity conditions to calculate several descriptive statistics of the noon NmF2 for each month, including the mathematical expectation, most probable value, arithmetic average, and arithmetic average median. The month-to-month variability of these descriptors allowed us to identify months of a year when they reach their extremes (maxima, minima). The calculated month-to-month variations of the NmF2 statistical parameters made it possible to study the winter anomaly and spring-autumn asymmetry in these statistical parameters.

  20. Whistler-mode chorus waves in the dayside outer magnetosphere under quiet geomagnetic conditions: PENGUIn-AGO and THEMIS conjugate observations

    NASA Astrophysics Data System (ADS)

    Keika, K.; Spasojevic, M.; Li, W.; Bortnik, J.; Miyoshi, Y.; Angelopoulos, V.; Gerrard, A. J.

    2011-12-01

    We perform a case study of whistler-mode chorus waves in the dayside outer (L>7) magnetosphere under quiet geomagnetic conditions. We use simultaneous conjugate observations made at 1230-1930 UT on 26 July 2008 by three THEMIS spacecraft and ground-based VLF receivers at two automatic geophysical observatories (AGO) in Antarctica supported by the US Polar Experiment Network for Geospace Upper-atmosphere Investigations (PENGUIn) project. Solar wind dynamic pressure was constant and weak (~1 nPa); the Dst index was around -10 nT; and the AE index showed weak activity (<200 nT). VLF wave intensification was observed by THEMIS A, D, and E. Waveform data from THEMIS A show that the waves were intensified in a frequency range of 500-800 Hz (0.3-0.4 fce) and circularly right-handed polarized. Filter bank data show that all three THEMIS probes observed wave intensification in the 287-1240 Hz range around noon and 6-9 RE near the equatorial plane. VLF signals at the AGO P2 station (AP2: MLAT = -76.6 deg.; MLT = UT-3.5h) were intensified in the frequency range of 500-1000 Hz. At the AGO P3 station (AP3: MLAT = -83.63 deg., MLT = UT-2h), VLF signals were intensified in the same frequency range; the increase rate was smaller than at AP2. The VLF wave intensification peaked around noon. The AGO AP2 and AP3 stations are mapped along field lines to the outer magnetosphere; the mapped locations in the equatorial plane are 9-10 RE and 10-11 RE around noon, respectively. We also confirm, from fluxgate magnetometer data, that AP2 and AP3 were equatorward of the open-closed boundary. The observed chorus waves were intensified in narrow ranges of MLT and radial distance. We conclude that the localized intensification continued for at least 1.5 hours. We examine the configuration of magnetic field lines in which the THEMIS spacecraft and the AGO stations reside during the wave intensification, and find that the intensification occurred when field lines have small gradient along a field

  1. Field-aligned neutral wind bias correction scheme for global ionospheric modeling at midlatitudes by assimilating FORMOSAT-3/COSMIC hmF2 data under geomagnetically quiet conditions

    NASA Astrophysics Data System (ADS)

    Sun, Yang-Yi; Matsuo, Tomoko; Maruyama, Naomi; Liu, Jann-Yenq

    2015-04-01

    This study demonstrates the usage of a data assimilation procedure, which ingests the FORMOSAT-3/COSMIC (F3/C) hmF2 observations to correct the model wind biases to enhance the capability of the new global Ionosphere Plasmasphere Electrodynamics (IPE) model under geomagnetically quiet conditions. The IPE model is built upon the field line interhemispheric plasma model with a realistic geomagnetic field model and empirical model drivers. The hmF2 observed by the F3/C radio occultation technique is utilized to adjust global thermospheric field-aligned neutral winds (i.e., a component of the thermospheric neutral wind parallel to the magnetic field) at midlatitudes according to a linear relationship between time differentials of the field-aligned wind and hmF2. The adjusted winds are further applied to drive the IPE model. The comparison of the modeled electron density with the observations of F3/C and ground-based GPS receivers at the 2012 March equinox suggests that the modeled electron density can be significantly improved in the midlatitude regions of the Southern Hemisphere, if the wind correction scheme is applied. Moreover, the F3/C observation, the IPE model, and the wind bias correction scheme are applied to study the 2012 Southern Hemisphere Midlatitude Summer Nighttime Anomaly (southern MSNA)/Weddell Sea Anomaly (WSA) event at December solstice for examining the role of the neutral winds in controlling the longitudinal variation of the southern MSNA/WSA behavior. With the help of the wind bias correction scheme, the IPE model better tracks the F3/C-observed eastward movement of the southern MSNA/WSA feature. The apparent eastward movement of the southern MSNA/WSA features in the local time coordinate is primarily caused by the longitudinal variation in the declination angle of the geomagnetic field that controls the field-aligned projection of both geographic meridional and zonal components of the neutral wind. Both the IPE simulations and the F3/C

  2. 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.

  3. Magnetic Signatures of Ionospheric and Magnetospheric Current Systems During Geomagnetic Quiet Conditions—An Overview

    NASA Astrophysics Data System (ADS)

    Olsen, Nils; Stolle, Claudia

    2016-09-01

    High-precision magnetic measurements taken by LEO satellites (flying at altitudes between 300 and 800 km) allow for studying the ionospheric and magnetospheric processes and electric currents that causes only weak magnetic signature of a few nanotesla during geomagnetic quiet conditions. Of particular importance for this endeavour are multipoint observations in space, such as provided by the Swarm satellite constellation mission, in order to better characterize the space-time-structure of the current systems. Focusing on geomagnetic quiet conditions, we provide an overview of ionospheric and magnetospheric sources and illustrate their magnetic signatures with Swarm satellite observations.

  4. Dependences of the NmF2 midlatitude statistical characteristics on the month of a year under geomagnetically quiet conditions near noon at low solar activity

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    The month-to-month variations in the statistical characteristics of the electron density at the mid-latitude ionospheric F2 layer maximum ( NmF2) were studied for geomagnetically quiet conditions near noon. The ionospheric F2 layer critical frequencies, measured by ionosondes in Ashkhabad, Tashkent, Rostov, Irkutsk, Moscow, Sverdlovsk, Tomsk, and Magadan at low solar activity from 1957 to 2013, were used in the performed statistical analysis. The mathematical expectation and the arithmetical mean value of NmF2, the arithmetical mean value of the NmF2 median, and the most probable NmF2 value were calculated for each month. The months with local extremums of these NmF2 statistical characteristics were indicated. It was demonstrated that the semiannual symmetry in the implementation time of local maximums of the NmF2 mathematical expectation, arithmetical mean values, and mean median is observed in the month-to-month variations over Ashkhabad, Tashkent, and Sverdlovsk. The semiannual symmetry of the most probable NmF2 value was found over Ashkhabad. The NmF2 statistical characteristics were compared with one another for each ionosonde at a fixed month. This comparison shows that the values of the most probable NmF2 and the NmF2 mathematical expectation and arithmetically mean median can pronouncedly differ from one another, and the maximal difference of the NmF2 mathematical expectation from the NmF2 arithmetical mean is 0.9%.

  5. A comparison of FUV dayglows measured by STSAT-1/FIMS with the AURIC model in a geomagnetic quiet condition

    NASA Astrophysics Data System (ADS)

    Kam, Hosik; Kim, Yong Ha; Hong, Jun-Seok; Lee, Joon-Chan; Choi, Yeon-Ju; Min, Kyung Wook

    2014-09-01

    The Korea scientific microsatellite, STSAT-1 (Science and Technology Satellite-1), was launched in 2003 and observed far ultraviolet (FUV) airglow from the upper atmosphere with a Far-ultraviolet IMaging Spectrograph (FIMS) at an altitude of 690 km. The FIMS consists of a dual-band imaging spectrograph of 900-1150 Å (S-band) and 1340-1715 Å (L-band). Limb scanning observations were performed only at the S-band, resulting in intensity profiles of OI 989 Å, OI 1026 Å, NII 1085 Å and NI 1134 Å emission lines near the horizon. We compare these emission intensities with those computed by using a theoretical model, the AURIC (Atmospheric Ultraviolet Radiance Integrated Code). The intensities of the OI 1026 Å, NII 1085 Å and NI 1134 Å emissions measured by using the FIMS are overall consistent with the values computed by using AURIC under the thermospheric and solar activity conditions on August 6, 1984, which is close to the FIMS's observation condition. We find that the FIMS dayglow intensity profiles match reasonably well with AURIC intensity profiles for the MSIS90 oxygen atom density profiles within factors of 0.5 and 2. However, the FIMS intensities of the OI 989 Å line are about 2 ˜ 4 times stronger than the AURIC intensities, which is expected because AURIC does not properly simulate resonance scattering of airglow and solar photons at 989 Å by atomic oxygen in the thermosphere. We also find that the maximum tangential altitudes of the oxygen bearing dayglows (OI 989 Å, OI 1026 Å) are higher than those of the nitrogen-bearing dayglows (NII 1085 Å, NI 1134 Å), which is confirmed by using AURIC model calculations. This is expected because the oxygen atoms are distributed at higher altitudes in the thermosphere than the nitrogen molecules. Validations of the qualities of both the FIMS instrument and the AURIC model indicate that AURIC should be updated with improved thermospheric models and with measured solar FUV spectra for better agreement with the

  6. Quiet geomagnetic field representation for all days and latitudes

    USGS Publications Warehouse

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

    1992-01-01

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

  7. 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.

  8. Magnetic Signatures of Ionospheric and Magnetospheric Current Systems During Geomagnetic Quiet Conditions—An Overview

    NASA Astrophysics Data System (ADS)

    Olsen, Nils; Stolle, Claudia

    2017-03-01

    High-precision magnetic measurements taken by LEO satellites (flying at altitudes between 300 and 800 km) allow for studying the ionospheric and magnetospheric processes and electric currents that causes only weak magnetic signature of a few nanotesla during geomagnetic quiet conditions. Of particular importance for this endeavour are multipoint observations in space, such as provided by the Swarm satellite constellation mission, in order to better characterize the space-time-structure of the current systems.

  9. Different Responses of Solar Wind and Geomagnetism to Solar Activity during Quiet and Active Periods

    NASA Astrophysics Data System (ADS)

    Kim, Roksoon; Park, J.-Y.; Baek, J.-H.; Kim, B.-G.

    2017-08-01

    It is well known that there are good relations of coronal hole (CH) parameters such as the size, location, and magnetic field strength to the solar wind conditions and the geomagnetic storms. Especially in the minimum phase of solar cycle, CHs in mid- or low-latitude are one of major drivers for geomagnetic storms, since they form corotating interaction regions (CIRs). By adopting the method of Vrsnak et al. (2007), the Space Weather Research Center (SWRC) in Korea Astronomy and Space Science Institute (KASI) has done daily forecast of solar wind speed and Dst index from 2010. Through years of experience, we realize that the geomagnetic storms caused by CHs have different characteristics from those by CMEs. Thus, we statistically analyze the characteristics and causality of the geomagnetic storms by the CHs rather than the CMEs with dataset obtained during the solar activity was very low. For this, we examine the CH properties, solar wind parameters as well as geomagnetic storm indices. As the first result, we show the different trends of the solar wind parameters and geomagnetic indices depending on the degree of solar activity represented by CH (quiet) or sunspot number (SSN) in the active region (active) and then we evaluate our forecasts using CH information and suggest several ideas to improve forecasting capability.

  10. Long-term monthly statistics of the mid-latitude ionospheric E-layer peak electron density in the Northern geographic hemisphere during geomagnetically quiet and steadily low solar activity conditions

    NASA Astrophysics Data System (ADS)

    Pavlov, Anatoli; Pavlova, Nadezhda

    2016-07-01

    Long-term hourly values of the ionospheric E-layer peak electron density, NmE, measured during the time period of 1957-2014 by 4 mid-latitude ionosondes (Wallops Island, Boulder, de l'Ebre, and Rome) in the Northern geographic hemisphere were processed to select periods of geomagnetically quiet and low solar activity conditions to calculate several descriptive statistics of NmE close to noon for each month in a year, including the mathematical expectation of NmE, the standard deviations of NmE from the mathematically expected NmE, and the NmE variation coefficient. The month-to-month variability of these descriptors allowed us to identify months of a year when they reach their extremes (maxima, minima). We found that the most probable NmE cannot be considered as the best statistical parameter among the most probable NmE and the mathematically expected NmE in statistical studies of month-to-month variations of NmE. Depending on a choice of an ionosonde and a month, the calculated NmE variation coefficient changes from 5 to 12 %.

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

    NASA Astrophysics Data System (ADS)

    Oh, Suyeon

    2013-03-01

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

  12. Achievement of a short term three dimensional electron density mapping of the ionosphere in the European sector: Comparisons with the IRI model for quiet-moderate geomagnetic-ionospheric conditions

    NASA Astrophysics Data System (ADS)

    Pietrella, M.

    2016-10-01

    In this paper will be described the procedure followed for the achievement of a short term three dimensional (3-D) electron density mapping of the ionosphere in the European area. It consists of three main steps: (1) foF2 and M(3000)F2 short-term forecasts, (foF2STF) and (M3000F2STF), are calculated at 12 ionospheric observatories scattered in the European area; (2) the values of foF2STF and M3000F2STF on a grid of equi-spaced points, (foF2STF,GP) and (M3000F2STF,GP), are calculated by means of an appropriate interpolation algorithm by using the foF2STF and M3000F2STF data; (3) foF2STF,GP and M3000F2STF,GP data ingestion into the IRI model is employed to produce a short term 3-D electron density mapping (ST-3D-M) of the ionosphere. The electron density profiles provided by the ST-3D-M and IRI models, were compared with the electron density profiles autoscaled by the Automatic Real-Time Ionogram Scaler with True-height (ARTIST) system, which are here considered as the truth profiles. The results of these comparisons, shown for a certain number of epochs during quiet-moderate geomagnetic-ionospheric conditions, in the truth-sites of Athens (38○.0‧N, 23○.5‧E), Chilton (51○.5‧N, -0○.6‧W), Dourbes (50○.1‧ N, 4○.6‧E), Pruhonice (50○.0‧N, 14○.6‧E), Rome (41○.9‧N, 12○.5‧E), and Tortosa (40○.8‧N, 0○.5‧E), indicate that the ST-3D-M as forecasting tool can be considered generally reliable.

  13. 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.

  14. Time-causal decomposition of geomagnetic time series into secular variation, solar quiet, and disturbance signals

    USGS Publications Warehouse

    Rigler, E. Joshua

    2017-04-26

    A theoretical basis and prototype numerical algorithm are provided that decompose regular time series of geomagnetic observations into three components: secular variation; solar quiet, and disturbance. Respectively, these three components correspond roughly to slow changes in the Earth’s internal magnetic field, periodic daily variations caused by quasi-stationary (with respect to the sun) electrical current systems in the Earth’s magnetosphere, and episodic perturbations to the geomagnetic baseline that are typically driven by fluctuations in a solar wind that interacts electromagnetically with the Earth’s magnetosphere. In contrast to similar algorithms applied to geomagnetic data in the past, this one addresses the issue of real time data acquisition directly by applying a time-causal, exponential smoother with “seasonal corrections” to the data as soon as they become available.

  15. Auroral forms that extend equatorward from the persistent midday aurora during geomagnetically quiet periods

    NASA Astrophysics Data System (ADS)

    Rodriguez, J. V.; Carlson, H. C.; Heelis, R. A.

    2012-09-01

    Auroral forms (“crewcuts”) that extend equatorward from the geomagnetically east-west aligned persistent midday aurora have been characterized based on a survey of Svalbard 630.0-nm all-sky images from eight December solstice seasons. The 630.0-nm forms are directly related to a mix of precipitating magnetosheath and plasma sheet electrons embedded in a population of boundary layer ions, as observed by NOAA 6. The associated midday aurora lies at the equatorward edge of poleward velocity-dispersed cusp ‘ion plumes’ observed by DMSP F7 at 1000 magnetic local time. In this survey, crewcuts are found to occur for Kp≤3. Distinct in many salient ways (including dynamics, orientation and associated IMF polarity) from the poleward-moving auroral forms (PMAFs) associated with transient dayside merging, crewcuts represent a solar wind-magnetosphere interaction that is more characteristic of quiet geomagnetic conditions. Crewcuts are present on 44% of the days for which all-sky images are complete and observing conditions are clear ±1.5 h around geomagnetic noon. During these periods, crewcuts are observed during 10.6% of the minutes for which IMF data from ISEE 2 or IMP 8 are available. We derive from the data a simple set of IMF “search criteria” that maximize the likelihood of observing crewcuts around the December solstice. The IMF magnitude range for which crewcuts are most commonly observed is 3.5±0.5 nT (36%). The IMF GSM component ranges in which crewcuts are most commonly observed are: Bx=-3.5±0.5 nT (27%), By=-1.5±0.5 nT (25%), and Bz=0.5±0.5 nT (26%). The IMF clock angular ranges for which crewcuts are most commonly observed are -70°±10° and 90°±10° (both 21%). The IMF cone angular range for which crewcuts are most commonly observed is 12.5°±2.5° (28%). Considering these observations in the context of magnetic merging topologies, we suggest crewcuts observed at Svalbard are most likely to lie at the foot of overdraped field lines

  16. Observations of intense ULF pulsation activity near the geomagnetic equator during quiet times

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.; Zanetti, L. J.; Potemra, T. A.; Klumpar, D. M.; Strangeway, R. J.; Acuna, M. H.

    1988-01-01

    This paper analyzes observations, made by particle and field instruments on the AMPTE CCE satellite, of intense ULF pulsations in the earth's magnetosphere near the geomagnetic equator. These pulsations were observed during magnetically quiet periods in regions characterized by intense fluxes of warm strongly trapped light ions, predominantly H(+), and often with streaming low-energy plasma. The strong latitudinal localization of these pulsations is interpreted to be due to equatorial mass loading or to partial reflection of Alfven wave energy by latitudinal gradients in plasma density. Possible sources of wave energy for these events are discussed.

  17. Some effects of quiet geomagnetic field changes upon values used for main field modeling

    USGS Publications Warehouse

    Campbell, W.H.

    1987-01-01

    The effects of three methods of data selection upon the assumed main field levels for geomagnetic observatory records used in main field modeling were investigated for a year of very low solar-terrestrial activity. The first method concerned the differences between the year's average of quiet day field values and the average of all values during the year. For H these differences were 2-3 gammas, for D they were -0.04 to -0.12???, for Z the differences were negligible. The second method of selection concerned the effects of the daytime internal Sq variations upon the daily mean values of field. The midnight field levels when the Sq currents were a minimum deviated from the daily mean levels by as much as 4-7 gammas in H and Z but were negligible for D. The third method of selection was designed to avoid the annual and semi-annual quiet level changes of field caused by the seasonal changes in the magnetosphere. Contributions from these changes were found to be as much as 4-7 gammas in quiet years and expected to be greater than 10 gammas in active years. Suggestions for improved methods of improved data selection in main field modeling are given. ?? 1987.

  18. Can the comprehensive model phase 4 (CM4) predict the geomagnetic diurnal field for days away from quiet time?

    NASA Astrophysics Data System (ADS)

    Onovughe, Elvis

    2016-10-01

    The most recent comprehensive model (CM4) of the geomagnetic field (Sabaka et al., 2004) has been used in conjunction with geomagnetic ground observatory station data to analyse and study the geomagnetic diurnal variation field for days away from quiet time and the CM4 prediction for these times. Even though much has been learnt about many components of the geomagnetic field, the diurnal variation field behaviour for days away from quiet time (moderately disturbed time) has not been intensively studied. Consequently, we analyse these, and the predictive ability of the CM4 for ground variations, and whether the CM4 prediction of the diurnal variation (whether at quiet time or away from quiet time) is valid outside the period of reference that from which the data were used in modelling. In carrying out the study, we compared the observatory station data and the CM4 prediction directly. Using the CM4 code, well-characterised internal and magnetospheric components were subtracted from the data, plots and global maps of the residual field generated and then compared with the CM4 to see how well the model performed in predicting the data at moderately disturbed time (Kp ≤ 5). The results show that the CM4 is valid and produces useful predictions outside the period covering the timespan of the model and during moderately disturbed time, despite the lack of active data in the original model dataset. The model predictability of the data increases as we move to higher spherical harmonic degree truncation, as the model-data misfit is reduced, but with increased roughness as a result of small-scale features incorporated. The observed results show that this relationship between the increase in spherical harmonic degree truncation and reduction in misfit can be restricted by data quality or quantity and global coverage or spread.

  19. Seasonal and solar activity dependence of the ionospheric electric fields estimated with geomagnetic solar quiet daily variation

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    In order to investigate the seasonal and solar activity dependence of the ionospheric electric field estimated with the geomagnetic solar quiet (Sq) daily variation from 1958 to 2015, we analyzed 1-hour geomagnetic field data obtained from 83 geomagnetic observatories from the middle-latitude to equatorial regions with an aid of the IUGONET data analysis tool. These geomagnetic field data were provided by WDC for Geomagnetism, Kyoto University. In this analysis, we first selected geomagnetic field data corresponding to a period of the solar quiet day when the Kp index is less than 4 throughout a day. Next, we identified the Sq variation as a deviation from the value at midnight in both the X and Y components of the geomagnetic field data. Finally, we obtained the monthly-mean ionospheric electric fields by solving Ohm's equation with the two-dimensional height-integrated ionospheric conductivity and geomagnetic Sq variation. As a result, the ionospheric zonal and meridional electric fields shows a clear seasonal variation and 11-year solar activity dependence for all of the investigated geomagnetic stations. The power spectra of the zonal electric field shows three dominant peaks at 6, 12 and 132 months. Moreover, the 4-month periodic component was also found in the middle-latitude regions. The intensity of the zonal electric field is positively correlated with the F10.7 index near the equatorial region (|θ| < 20 degrees, θ: magnetic latitude) with no time lag while it is negatively correlated in the middle-latitude region (|θ| > 20 degrees). The latitudinal difference of the correlation coefficient between the F10.7 index and the zonal electric field intensity is seen over the entire range of geographic longitude analyzed in this study. As a cause of the negative correlation in the middle latitudes, it can be thought that the neutral wind originating from solar tidal waves in the lower thermosphere becomes weaker during a high solar activity due to the

  20. Influence of Geomagnetic and IMF conditions on High Latitude Upper Atmospheric winds and Temperatures

    NASA Astrophysics Data System (ADS)

    Dhadly, M. S.; Conde, M.; Emmert, J. T.

    2015-12-01

    We analyzed the climatological behavior of upper atmospheric winds (horizontal and vertical) and temperatures above Alaska by combining line-of-sight Doppler shifts of 630 nm optical emissions recorded during the 2011 and 2012 winters using a ground based all-sky wavelength scanning Doppler Fabry-Perot interferometer (SDI) located at Poker Flat (65.12N, 147.47W). The wide field of view covered a large geographic region above Alaska. This field was divided in software into multiple zones (115 used here), allowing independent spectra to be sampled from many directions simultaneously. As a result, it is capable of recording the wind field's spatial variations over a wide geographic region with high spatial resolution, and to resolve these variations over time. Although such climatological studies have been performed previously using satellites, models, and narrow field Fabry-Perot interferometers, there are no published climatological studies of thermospheric winds and temperatures using either SDI data or any other technique with comparable geographic coverage and resolution. Wind summary dial plots were produced to depict the climatology of the horizontal winds and temperatures for different geomagnetic conditions and orientation of interplanetary magnetic field (IMF). Results show that horizontal winds and temperatures had a strong dependence on geospace activity and orientation of IMF. The latitudinal shears in horizontal winds were stronger when geomagnetic conditions were active compared to the latitudinal shears for quiet conditions. Also, shears appeared earlier over Poker Flat when geomagnetic conditions were active. The latitudinal shears showed more dependence on IMF when geomagnetic conditions were active than they did during quieter conditions. F-region temperatures were higher under active geomagnetic conditions than during quiet conditions. They were also observed to be higher in pre-magnetic midnight sector (duskside) than they were post

  1. Mapping Geomagnetic Field Variations in the Cretaceous Quiet Zone with Unmanned Airborne Vehicles

    NASA Astrophysics Data System (ADS)

    Gee, J. S.; Cande, S. C.; Kent, D. V.

    2007-12-01

    About one quarter of the present seafloor was generated during the constant normal polarity interval from 121 to 83 Ma (Cretaceous Quiet Zone or KQZ), and the lack of temporal markers limits tectonic reconstructions in these areas. Although magnetostratigraphic studies provide strong evidence that the KQZ formed during predominantly normal polarity, there are nonetheless relatively large amplitude variations in many sea surface magnetic anomaly profiles crossing KQZ crust. To evaluate the relative importance of geomagnetic and crustal variables (thickness, geochemistry) in generating these anomalies, we collected multibeam bathymetry and magnetic data on 19 profiles crossing anomaly 34 and extending 500 km into the KQZ in the southwest Pacific. The relatively fast spreading (60 km/m.y. half rate), minimal sediment cover and high paleolatitude of formation make this area ideal for evaluating the magnetic anomaly pattern. An additional 10,000 km of magnetic anomaly data were acquired using an autonomous unmanned airborne vehicle (UAV). Although land-launched UAVs have been used in a variety of research applications, the nine successful flights during our cruise represent the first deployment from a UNOLS research vessel. The UAV (operated by Fugro Airborne) was launched from a pneumatic catapult and captured by a wingtip clip that attaches to a rope suspended from a retractable boom on the fantail. The Cs-vapor magnetometer data from the UAV compare favorably with results from the surface-towed magnetometer, with minor differences related primarily to the higher elevation (120m above sea level) of the UAV. The resulting magnetic coverage indicates that, as with younger seafloor, quasi-linear short wavelength anomalies are present within the KQZ. These anomalies can vary on spatial scales smaller than the multibeam swath width, highlighting the utility of obtaining additional coverage with the UAVs.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  4. Revisiting geomagnetic activity at auroral latitudes: No need for regular quiet curve removal for geomagnetic activity indices based on hourly data

    NASA Astrophysics Data System (ADS)

    Martini, Daniel; Argese, Chiara; Di Loreto, Massimo; Mursula, Kalevi

    2016-07-01

    The main objective of our study is to determine if the regular quiet daily curve (QDC) subtraction is a necessary procedure in quantifying the irregular geomagnetic variations at auroral latitudes. We define the hourly ΔH index, the absolute hour-to-hour deviation in nanotesla of the hourly geomagnetic horizontal component, which assigns each sample to sample deviation as geomagnetic activity without separating the "regular" and "irregular" parts of the daily magnetic field evolution. We demonstrate that the hourly gradient of the regular Sq variation is very small with respect to the irregular part, and a bulk of the nominal daily variation is actually part of the variation driven by solar wind and interplanetary magnetic field and traditionally classified as irregular. Therefore, attempts to subtract QDC can lead to a larger error, often caused by residual deviations between the used different mathematical and methodological tools and corresponding presumptions themselves. We show that ΔH provides the best and most consistent results at most timescales with the highest effective resolution among the studied indices. We also demonstrate that the ΔH index may equally be useful as a quick-look near-real-time index of space weather and as a long-term index derived from hourly magnetometer data for space climate studies.

  5. Thermospheric/ionospheric disturbances under quiet and magneto-perturbed conditions

    NASA Astrophysics Data System (ADS)

    Zakharov, Ivan G.; Mozgovaya, O. L.

    2003-04-01

    The basic mechanisms of ionospheric storms (IS) are investigated sufficiently full. Despite of it a quantitative forecast of ionospheric disturbance is not always satisfactory. One of the possible causes can be related to the insufficient account of a background ionospheric. In particualr using electron concentration Ne in the peak of F2-region and total electron content are shown, that the amplitude of a IS positive phase for similar magnetic storms can differ by ~1,5 times. Hence a cause of distinction can be variations in the thermosphere conditions, not reflected by known activity indices. For further research we used the incoherent scatter radar data of the Institute of ionosphere in height range 200-1000 km in the very quiet periods coming to the geomagnetic disturbance. A steady periodic disturbance in Ne during quiet conditions in all heights is established, which can be identified as tidal moda m=6. The amplitude of wave is ~15%, the phase changes with a height. The storm onset leads to an increase of the amplitudes approximately twice without a change in the phase. An ionospheric disturbance in very quiet conditions can lead to additional complicating an ionosphere reaction to magnetic storm.

  6. Long-term variation in the ionosphere and lower thermosphere as seen in the geomagnetic solar quiet daily variation

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    In order to investigate characteristics of the long-term variation in the ionosphere and lower thermosphere, we analyzed the amplitude of geomagnetic solar quiet (Sq) field daily variation using 1-h geomagnetic field data obtained from 69 geomagnetic stations within the period of 1947-2013. In the present data analysis, we took advantage of the Inter-university Upper atmosphere Global Observation NETwork (IUGONET) products (metadata database and analysis software) for finding and handling the long-term observation data obtained at many observatories. The Sq amplitude observed at these geomagnetic stations showed a clear solar activity dependence and tended to be enhanced during each solar maximum phase. The Sq amplitude was the smallest around the minimum of solar cycle 23/24 in 2008-2009. This significant depression implies that the solar extreme ultraviolet (EUV) radiation responsible for ionization of the upper atmosphere decreased during this solar cycle minimum. In order to examine a global distribution of the long-term trend in the Sq amplitude, we derived the residual Sq amplitude from the deviation from the fitting curve between the solar F10.7 index and Sq amplitude. As a result, a majority of the trends in the residual Sq amplitude showed negative values over a wide region. This tendency was relatively strong in Europe, India, the eastern part of Canada, and New Zealand. Moreover, we estimate the neutral wind in the lower thermosphere from the Sq amplitude and height-integrated ionospheric conductivity in order to know the physical mechanism of the long-term trend in the residual Sq amplitude. As a result, the estimated thermospheric zonal and meridional winds showed a seasonal variation with a period of one year or less, but the solar activity dependence was unclear. This result suggests that the solar cycle dependence of the Sq amplitude may be mainly attributed to the variation of the ionospheric conductivity.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  9. Simultaneous observation of whistlers and emissions during a geomagnetically quiet period at low latitude

    NASA Astrophysics Data System (ADS)

    Singh, Ashutosh K.; Singh, K. K.; Singh, A. K.; Lalmani

    2011-02-01

    A unique night-time natural electromagnetic disturbances in the VLF/ELF range received during a magnetically quite period at a low latitude Indian ground station, Jammu (geomag. lat. 19°26' N, L=1.17) has been reported. During the routine observation of VLF waves at Jammu, whistlers and different types of VLF/ELF emissions such as whistlers of varying dispersion confined to a small band limited frequency range, hisslers, pulsing hiss, discrete chorus emissions of rising and falling tones with multiple bands, oscillating tone discrete emission, whistler-triggered hook and discrete chorus risers emissions, etc. have been observed simultaneously during the quiet period on a single night. Such type of unique simultaneous observations has never been reported from any of the low latitude ground stations and this is the first observation of its kind. The results are discussed in the light of recorded features of whistlers and emissions. Generation and propagation mechanism are discussed briefly. Plasma parameters are further derived from the dispersion analysis of nighttime whistlers and emissions recorded simultaneously during magnetically quiet periods.

  10. Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times.

    PubMed

    Shi, Q Q; Zong, Q-G; Fu, S Y; Dunlop, M W; Pu, Z Y; Parks, G K; Wei, Y; Li, W H; Zhang, H; Nowada, M; Wang, Y B; Sun, W J; Xiao, T; Reme, H; Carr, C; Fazakerley, A N; Lucek, E

    2013-01-01

    An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times.

  11. Forecasting Geomagnetic Conditions in near-Earth space

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    It has been well-known that geomagnetic solar quiet (Sq) daily variation is produced by global ionospheric currents flowing in the E-region from middle latitudes to the magnetic equator. These currents are generated by a dynamo process via interaction between the neutral wind and ionospheric plasma in a region of the thermosphere and ionosphere. From the Ohm's equation, the ionospheric currents strongly depend on the ionospheric conductivity, polarization electric field and neutral wind. Then, to investigate the Sq amplitude is essential for understanding the long-term variations in the ionospheric conductivity and neutral wind of the thermosphere and ionosphere. Elias et al. [2010] found that the Sq amplitude tends to increase by 5.4-9.9 % in the middle latitudes from 1961 to 2001. They mentioned that the long-term variation of ionospheric conductivity associated with geomagnetic secular variation mainly determines the Sq trend, but that the rest component is ionospheric conductivity enhancement associated with cooling effects in the thermosphere due to increasing the greenhouse gases. In this talk, we clarify the characteristics of the long-term variation in the Sq amplitude using the long-term observation data of geomagnetic field and neutral wind. These observation data have been provided by the IUGONET (Inter-university Upper atmosphere Global Observation NETwork) project. In the present analysis, we used the F10.7 flux as an indicator of the variation in the solar irradiance in the EUV and UV range, geomagnetic field data with time resolution of 1 hour. The definition of the Sq amplitude is the difference of the H-component between the maximum and minimum per day when the Kp index is less than 4. As a result, the Sq amplitude at all the stations strongly depends on 11-year solar activity, and tends to enhance more during the high activities (19- and 22- solar cycles) than during the low activity (20-solar cycle). The Fourier spectra of the F10.7 flux and Sq

  13. Low-latitude daytime F region irregularities observed in two geomagnetically quiet days by the Hainan coherent scatter phased array radar (HCOPAR)

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Jin, Han; Yan, Jingye; Zhang, Shaodong; Li, Guozhu; Yokoyama, Tatsuhiro; Yang, Guotao; Yan, Chunxiao; Wu, Chen; Wang, Jin; Zhong, Dingkun; Li, Yaxian; Wang, Zhihua

    2017-02-01

    Hainan coherent scatter phased array radar (HCOPAR) located at low latitude of China has recorded the extremely rare daytime F region irregularities at noon of 22 July 2013 and 23 May 2016. The two field-aligned irregularities (FAIs) appeared in the topside F2 layer and presented small Doppler velocities and narrow spectral widths. The fan sector maps show that the FAIs moved northward with almost no zonal speed. The irregularities emerged in the geomagnetically quiet condition and were irrelevant to the storm-induced eastward electric field as other daytime cases. More than 2 h after the emergency of the daytime irregularities over Hainan, the Shaoyang digisonde situated 870 km north to the HCOPAR recorded the spread-F in ionospheric F1 layer. According to the echo altitudes, the spread-F may connect the daytime bubbles via magnetic field line. The strong photoionization after sunrise made it difficult to generate the plasma bubbles in the sunlit ionosphere. Consequently, the two midday FAIs over Hainan may drift along the magnetic field lines from higher altitudes in the south and are most likely the remnant of previous night's bubbles.

  14. 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.

  15. Impact of Solar wind plasma parameters on geomagnetic condition

    NASA Astrophysics Data System (ADS)

    Rathore, Balveer Singh; Gupta, Dinesh Chandra

    Today’s challenge for space weather research is to quantitatively predict the dynamics of the magnetosphere from measured solar wind and interplanetary magnetic field conditions. A correlative studies between the Geomagnetic Storms (GMSs) and the various interplanetary field/plasma parameters have been performed to search the causes of geomagnetic activity and developing models for prediction of the occurrence of GMSs which are important for space weather predictions. In the present paper we found possible co-relation of geomagnetic storms with solar wind and IMF parameters in three different situations and also drive the linear relation equation for all parameters in three situations. On basis of present statistical study we developed an empirical model. With the help of this model we can predict all categories of geomagnetic storms. This model based on following fact. The total interplanetary magnetic field Btotal can use as alarm of geomagnetic storms, when sudden changes in total magnetic field B total, it is a first alarm on condition for storms arrival. It is observed in the present study that southward Bz-component of IMF is an important factor for geomagnetic storms. And it is the result of the paper that the magnitude of Bz is maximum neither during initial phase (at the instant of IP shock) nor during main phase (at the instant of Dst minimum). So it is seen in this study that there is a time delay between maximum value of southward Bz and Dst minimum and this time delay can be used in the prediction of the intensity of magnetic storm two -three hours before of main phase of geomagnetic storm. A linear relation have been derived between maximum value of southward component of Bz and Dst for prediction is Dst = (-0.06) + (7.65)Bz + t. Some auxiliary condition should be fulfils with this, speed of solar wind should be on average 350 km/s to 750 km/s, plasma beta should be low and most important plasma temperature should be low for intense storms if plasma

  16. Study of atomic oxygen greenline dayglow emission in thermosphere during geomagnetic storm conditions

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    The influence of geomagnetic storms on the atomic oxygen greenline (557.7 nm) dayglow emission in thermosphere is studied during solar active and solar quiet conditions. This study is primarily based on the photochemical model with inputs obtained from experimental observations and empirical models. The updated rate coefficients, quantum yields and related cross-sections have been used from experimental results and theoretical studies. This study is presented for a low latitude station Tirunelveli (8.7°N, 77.8°E), India. The volume emission rate (VER) has been calculated using densities and temperatures from the empirical models. The modeled VER shows a positive correlation with the Dst index. The VER also shows a negative correlation with the number densities of O, O2, and N2. The VER, calculated at peak emission altitude, exhibits depletion during the main phase of the storm. The altitude of peak emission rate is unaffected by the geomagnetic storm activity. The study also reveals that the peak emission altitude depends on the F10.7 solar index. The peak emission altitude moves upward as the value of F10.7 solar index increases.

  17. The Aurora at Quiet Magnetospheric Conditions: Repeatability and Dipole Tilt Angle Dependence

    DTIC Science & Technology

    1993-03-01

    A tial to variation of the dipole tilt angle. Wu et al. [1991] images of the aurora borealis obtained by Polar BEAR at studied the substorm westward... Aurora at Quiet Magnetospheric Conditions: SRepeatability and Dipole Tilt Angle Dependence PE 62101F _PR 4643 6. AUTHCR(S) TA 11 I. Oznovich*, R.W...tilt angle at quiet magnetospheric conditions? In order to address these questions, northern hemisphere images of the aurora at 1356 A, obtained by

  18. [VEGETATIVE REGULATORY MECHANISMS IN DIFFERENT GEOMAGNETIC CONDITIONS DEPENDING ON A DEGREE OF PHYSICAL CONDITIONING].

    PubMed

    Kvachadze, I; Tsibadze, A; Sanadiradze, G; Mzhavanadze, D; Chichinadze, G

    2016-04-01

    The aim of the study was to evaluate the vegetative regulatory action in healthy, untrained and trained individuals in different geomagnetic conditions. The study involved 94 healthy untrained young men aged 18-22 years - I group (control), and 60 trained volunteers aged 18-25 years - II group, who during the period of the study and for at least three years prior have been following active regular physical exercise regimen(weight lifting), but were not professional athletes. In order to evaluate the heart rate variability the following statistical indicators were studied: arithmetic mean, the arithmetic mean of the error variance, dispersion, the arithmetic mean deviation, coefficient of skewness, kurtosis, standard deviation of the mean. Geometric analysis was performed using a variation pulsometry. All the individuals were studied in natural/tranquil conditions, during naturally occuring or a simulated geomagnetic storm, which provided the use of the characteristics of vegetative balance as a marker for differential assessment of the impact of electromagnetic field (EMF). The forecast of natural geomagnetic conditions had been made at least three days before the study. Under the conditions of simulated geomagnetic storm the test subjects were placed in a solenoid with non-magnetic equipment. EMF inductance in the solenoid corresponded to the geomagnetic storm frequencies. The study had a nature of social experiment and was carried out by a single blind method: tested subjects were unaware of geomagnetic conditions during the study. This was an open, three-step, cohort, prospective study with parallel character. The results showed that under the uniform qualitative conditions (balanced, in particular) of initial state of vegetative equilibrium, the level of fitness of the human body determines the differentiated response to EMF exposure. Thus, with the possible inclusion of the EMF in the complex of therapeutic or preventive measures, it is necessary to predict

  19. Results of diurnal anisotropy in CR intensity on different geomagnetic conditions.

    NASA Astrophysics Data System (ADS)

    Dubey, S. K.; Kumar, S.; Agrawal, R.

    2001-08-01

    Cosmic Ray intensity data for a period of eleven years (1985-95; which covers descending phase of the 21st solar cycle and ascending phase of the 22nd solar cycle alongwith the maximum and minimum solar activity periods), have been analysed using four different criteria for selection of days for such analysis. Study of diurnal anisotropy on different criteria shows that the phase of diurnal anisotropy during 1985-91, remains constant within the statistical error limits and in the later period it shifts to early hours in 1992-93 and then it shifts further to earlier hours in 1994 and 95. It is also found that the characteristics of daily variation in cosmic ray intensity are quite comparable for all the four different groups of days, during the period of investigation. 1Introduction Association between the Cosmic Ray (CR) intensity and solar transients are well established and effects of changing interplanetary conditions in the interplanetary space are reflected in spatial distribution of CR intensity which also affect geomagnetic activity index Kp or Ap. The anisotropic modulation in CR intensity on long/short term basis has been studied for diurnal anisotropy and for higher harmonics in CR intensity, satisfying different criteria. Kumar et al (1981; 87; 93; 98) studied the diurnal anisotropy on geomagnetically quietestdays(60QD);Whereas,Rao(1972), Agrawal (1983); Bieber and Evanson (1997); Ahluwalia (1999) have opted All Days (AD) for such analysis. Agrawal (1981) considered to perform study over continuous periods, where the monthly mean values of diurnal amplitude and/or phase are significantly different as compared to the annual average values. This situation led to a search for the most suitable criteria for selection of days for analysis of CR intensity data. In the present paper, an attempt has been made to study the CR diurnal variation on the basis of different criteria. 2 Data Analysis Days with lowest values of Ap and Kp are identified as

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

    NASA Astrophysics Data System (ADS)

    Chu, W.; Qin, G.

    2016-01-01

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

  1. A preliminary comparison of Na lidar and meteor radar zonal winds during quiet and sub-storm conditions

    NASA Astrophysics Data System (ADS)

    Grandhi, Kishore Kumar; Nesse Tyssøy, Hilde; Williams, Bifford P.; Stober, Gunter

    2017-04-01

    It is speculated that sufficiently large electric fields during geomagnetic disturbed conditions may decouple the meteor trail electron motions from the background neutral winds and leads to erroneous neutral wind estimation. As per our knowledge, the potential errors have never been reported. In the present case study, we have been using co-located meteor radar and sodium resonance lidar zonal wind measurements over Andenes (69.27oN,16.04oE) during intense sub storms in the declining phase of Jan 2005 solar proton event (21-22 Jan 2005). In total 14 hours of continuous measurements are available for the comparison, which covers both quiet and disturbed conditions. For comparison, the lidar zonal winds are averaged in meteor radar time and height bins. High cross correlations (˜0.8) are found in all height regions. The discrepancies can be explained in the light of differences in the observational volumes of the two instruments. Further, we extended the comparison to address the ionization impact on the meteor radar winds. For quiet hours, the observed meteor radar winds are quite consistent with lidar winds. While during the disturbed hours comparatively large differences are noticed at higher most altitudes. This might be due to ionization impact on meteor radar winds. At the present one event is not sufficient to make any consolidate conclusion. However, at least from this study we found some effect on the neutral wind measurements for the meteor radar. Further study with more co-located measurements are needed to test statistical significance of the result.

  2. The geomagnetic storms of 2015: Statistical analysis and forecasting results

    NASA Astrophysics Data System (ADS)

    Paouris, Evangelos; Gerontidou, Maria; Mavromichalaki, Helen

    2016-04-01

    The year 2015 was characterized by long geomagnetic quiet periods with a lot of geomagnetically active breaks although it is on the declining phase of the current solar cycle. As a result a number of geomagnetic storms in the G1 up to G4 scale were noticed. In this work the characteristics of these geomagnetic storms like the scale level, the origin of the storm (CME or CIR) and the duration have been studied. Furthermore, a statistical analysis of these events and a comparative study of the forecasting and the actual geomagnetic conditions are performed using data from the NOAA space weather forecasting center and from the Athens Space Weather Forecasting Center as well. These forecasting centers estimate and provide every day the geomagnetic conditions for the upcoming days giving the values of the geomagnetic index Ap. The forecasting values of Ap index for the year 2015 from these two centers and their comparison in terms of the actual values are discussed.

  3. 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.

  4. Middle- and low-latitude emissions from energetic neutral atom precipitation seen from ATLAS 1 under quiet magnetic conditions

    NASA Technical Reports Server (NTRS)

    Tinsley, B. A.; Rohrbaugh, R. P.; Ishimoto, M.; Torr, M. R.; Torr, D. G.

    1994-01-01

    During the ATLAS 1 mission spectral observations were made at middle and low latitudes of features expected from the precipitation of energetic neutral atoms. The Imaging Spectrometric Observatory was used at night in the UV and visible with maximum gain. The tangent ray heights of the look directions ranged from near 100 km to near 200 km, and the geomagnetic conditions were quiet during the observations, which were made March 28 to April 3, 1992. The N2(+) 1N 391.4-nm and O I 130.4 and 135.6-nm emissions were observed at all latitudes, with lower emission rates at lower magnetic dip latitudes, except that enhancements in the O I lines were seen within 30 deg of the dip equator to radiative recombination of ionospheric plasma. The latitude profile observed for the N2(+) 1N emission did not show an equatorial or midlatitude peak. This implies that the source of energetic neutrals is more consistent with prompt charge exchange loss of freshly injected trapped ions with relatively low mirror heights (i.e., ions on higher L shells with equatorial pitch angle distributions nearly isotropic to the loss cone) than loss of highly eroded populations of particles with high mirror heights (i.e., ions on lower L shells with pancake equatorial pitch angle distributions). The N2(+) 1N emission rates have been compared with models of atmospheric emission due to fluxes of O/O(+) and H/H(+) in the thermosphere, as produced by energetic neutral oxygen or hydrogen atom precipitation. Energy deposition rates are inferred.

  5. Characteristics of long-term variation in the amlitude of the geomagnetic solar quiet (Sq) daily variation using the Inter-university Upper atmosphere Gobal Observation NETwork (IUGONET) data analysis system

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Characteristics of long-term variation in the amplitude of solar quiet geomagnetic field daily variation (Sq) have been investigated using 1-hour geomagnetic field data obtained from 69 geomagnetic stations in a period of 1947-2013. In the present data analysis, we took advantage of the IUGONET data analysis system. The Sq amplitude clearly showed a 10-12 year solar activity dependence and it tended to enhance during each solar maximum. During the minimum of solar cycle 23/24 in 2008-2009, the Sq amplitude became the smallest in the investigated period. The relationship between the solar F10.7 index and Sq amplitude is approximately linear but 64 percent of geomagnetic stations show a weak nonlinear dependence on the solar F10.7 index. In order to remove the effect of solar activity seen in the long-term variation of the Sq amplitude, we calculated a linear or second order fitting curve between the solar F10.7 index and Sq amplitude during 1947-2013, and examined the residual Sq amplitude, which is defined as the deviation from the fitting curve. As a result, a majority of the trends in the residual Sq amplitude that passed through a trend test showed a negative value in a wide region. This tendency was relatively strong in Europe, India, the eastern part of Canada, and New Zealand. The relationship between the magnetic field intensity and residual Sq amplitude showed an anti-correlation for about 71 percent of geomagnetic stations. On the other hand, the residual Sq amplitude in the equatorial station (Addis Ababa) was anti-correlated with the absolute value of the magnetic field inclination. This implies the movement of the equatorial electrojet due to the secular variation of the ambient magnetic field.

  6. Latitudinal and MLT dependence of the seasonal variation of geomagnetic field around auroral zone

    NASA Astrophysics Data System (ADS)

    Zhu, Jin; Du, Aimin; Ou, Jiaming; Xu, Wenyao

    2017-08-01

    Seasonal variation of geomagnetic field around auroral zone is analyzed in terms of geomagnetic latitude, magnetic local time (MLT) and geomagnetic condition in this study. The study uses horizontal component (H) of geomagnetic field obtained from 6 observatories located in geomagnetic latitude of 57.8°N-73.8°N along 115°E longitudinal line. The results indicate that seasonal variations of geomagnetic field around auroral zone are different combinations of annual and semiannual variations at different latitudinal ranges. Both annual and semiannual variations show distinct MLT dependency: (1) At dayside auroral latitudes (around 72°N geomagnetic latitude), geomagnetic field shows distinct annual variation under both quiet and disturbed conditions. Furthermore, the annual component is mainly contributed by data of dusk sector. (2) At nightside auroral latitudes (around 65°N), geomagnetic field shows semiannual dominated seasonal variation. Under quiet conditions the annual component is comparable to the semiannual component, while under disturbed conditions, the semiannual component is twice as much as the annual component. Under quiet conditions, the semiannual component is mainly contributed by 1300-1400 MLT, while the annual component has two peaks: one is around 1100-1300 MLT and the other is around 2000-2200 MLT. Under disturbed conditions, the semiannual component is mainly contributed by data around midnight, while the annual component is mainly contributed by dusk sector. (3) At subauroral latitudes (around 60°N), annual variation is comparable to semiannual variation under both quiet and disturbed conditions. Both annual and semiannual components show similar MLT dependencies as that of nightside auroral latitudes.

  7. 49 CFR 222.51 - Under what conditions will quiet zone status be terminated?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...-RAIL GRADE CROSSINGS Exceptions to the Use of the Locomotive Horn Silenced Horns at Groups of Crossings... SSM at every public crossing within the quiet zone or for quiet zones established by reducing the... Administrator a written commitment to lower the potential risk to the traveling public at the crossings...

  8. 49 CFR 222.51 - Under what conditions will quiet zone status be terminated?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...-RAIL GRADE CROSSINGS Exceptions to the Use of the Locomotive Horn Silenced Horns at Groups of Crossings... SSM at every public crossing within the quiet zone or for quiet zones established by reducing the... Administrator a written commitment to lower the potential risk to the traveling public at the crossings...

  9. 49 CFR 222.51 - Under what conditions will quiet zone status be terminated?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...-RAIL GRADE CROSSINGS Exceptions to the Use of the Locomotive Horn Silenced Horns at Groups of Crossings... SSM at every public crossing within the quiet zone or for quiet zones established by reducing the... Administrator a written commitment to lower the potential risk to the traveling public at the crossings...

  10. 49 CFR 222.51 - Under what conditions will quiet zone status be terminated?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...-RAIL GRADE CROSSINGS Exceptions to the Use of the Locomotive Horn Silenced Horns at Groups of Crossings... SSM at every public crossing within the quiet zone or for quiet zones established by reducing the... Administrator a written commitment to lower the potential risk to the traveling public at the crossings...

  11. 49 CFR 222.51 - Under what conditions will quiet zone status be terminated?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...-RAIL GRADE CROSSINGS Exceptions to the Use of the Locomotive Horn Silenced Horns at Groups of Crossings... SSM at every public crossing within the quiet zone or for quiet zones established by reducing the... Administrator a written commitment to lower the potential risk to the traveling public at the crossings...

  12. Locally adapted NeQuick 2 model performance in European middle latitude ionosphere under different solar, geomagnetic and seasonal conditions

    NASA Astrophysics Data System (ADS)

    Vuković, Josip; Kos, Tomislav

    2017-10-01

    model accuracy, during most of the disturbed periods the model could be used, but with lower accuracy than in the quiet geomagnetic conditions. The comprehensive analysis of locally adapted NeQuick 2 model performance highlighted the challenges of using the single point data ingestion applied to a large region in middle latitudes and determined the achievable radii for different error thresholds in various ionospheric conditions.

  13. Impact of active geomagnetic conditions on stimulated radiation during ionospheric second electron gyroharmonic heating

    NASA Astrophysics Data System (ADS)

    Bordikar, M. R.; Scales, W. A.; Mahmoudian, A.; Kim, H.; Bernhardt, P. A.; Redmon, R.; Samimi, A. R.; Brizcinski, S.; McCarrick, M. J.

    2014-01-01

    Recently, narrowband emissions ordered near the H+ (proton) gyrofrequency (fcH) were reported in the stimulated electromagnetic emission (SEE) spectrum during active geomagnetic conditions. This work presents new observations and theoretical analysis of these recently discovered emissions. These emission lines are observed in the stimulated electromagnetic emission (SEE) spectrum when the transmitter is tuned near the second electron gyroharmonic frequency (2fce) during recent ionospheric modification experiments at the High Frequency Active Auroral Research (HAARP) facility near Gakona, Alaska. The spectral lines are typically shifted below and above the pump wave frequency by harmonics of a frequency roughly 10% less than fcH (≈ 800 Hz) with a narrow emission bandwidth less than the O+ gyrofrequency (≈ 50 Hz). However, new observations and analysis of emission lines ordered by a frequency approximately 10% greater than fcH are presented here for the first time as well. The interaction altitude for the heating for all the observations is in the range of 160 km up to 200 km. As described previously, proton precipitation due to active geomagnetic conditions is considered as the reason for the presence of H+ ions known to be a minor background constituent in this altitude region. DMSP satellite observations over HAARP during the heating experiments and ground-based magnetometer and riometer data validate active geomagnetic conditions. The theory of parametric decay instability in multi-ion component plasma including H+ ions as a minority species described in previous work is expanded in light of simultaneously observed preexisting SEE features to interpret the newly reported observations. Impact of active geomagnetic conditions on the SEE spectrum as a diagnostic tool for proton precipitation event characterization is discussed.

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

    NASA Astrophysics Data System (ADS)

    Su, F.

    2014-12-01

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

  15. 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).

  16. Radar observations of magnetospheric activity during extremely quiet solar wind conditions

    NASA Astrophysics Data System (ADS)

    Walker, A. D. M.; Baker, K. B.; Pinnock, M.; Dudeney, J. R.; Rash, J. P. S.

    2002-04-01

    During a period of extremely quiet solar wind conditions from 8 to 10 March 1997, strong activity was observed by the Southern Hemisphere Auroral Radar Experiment Super Dual Auroral Radar Network radars in the Antarctic premidnight ionosphere. This activity took the form of quasiperiodic flow bursts with ionospheric drift velocities exceeding 2 km s-1. Data from the Satellite Experiments Simultaneous with Antarctic Measurements (SESAME) automated geophysical observatories in Antarctica and Defense Meteorological Satellite Program and Polar satellites are used with the radar data to study the convection flow in the southern polar ionosphere at the time of these flow bursts. The study shows that the bursts occurred with an approximate period of 12 min. Their direction was westward, and they were superimposed on a background westward flow. In the premidnight sector this is interpreted as a flow associated with dipolarization of the magnetotail tail field. There is a band of strong particle precipitation associated with the flow bursts. The location suggests that they occur deep in the magnetotail and cannot be associated with any lobe reconnection. They are at a latitude near the region where a viscously driven convection cell is expected to exist, and their sense is that of the return convection flow in such a cell. The results suggest that there is an internal magnetospheric mechanism for sporadic energy release in the magnetotail that need not be associated with changes in solar wind reconnection on the magnetopause.

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

    NASA Astrophysics Data System (ADS)

    Kaushik, Subhash Chandra

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

  18. Ionospheric manifestations of acoustic-gravity waves under quiet and disturbed conditions

    NASA Astrophysics Data System (ADS)

    Barabash, Vladimir; Chernogor, Leonid; Panasenko, Sergii; Domnin, Igor

    2014-05-01

    We present the observation results of wave disturbances in the ionosphere, which are known to be manifestations of atmospheric acoustic-gravity waves (AGWs). The observations have been conducted under quiet and naturally or artificially disturbed conditions by ionosonde and incoherent scatter radar located near Kharkiv, Ukraine. Wave disturbance parameters under quiet conditions were obtained and analysed during geophysical periods including vernal and autumn equinoxes as well as summer and winter solstices. The prevailing oscillation in ionospheric F2- layer had the period of 140 - 200 min and relative amplitude of 0.1 - 0.2. The duration of this oscillation changed from 5 - 7 to 24 hours, depending on a season. The amplitude of fluctuations with other periods was noticeably smaller. The time intervals at which the intensity of incoherent scatter signals varied quasi-periodically in the altitude range from 150 to 300 km were detected. The parameters of these variations were estimated using statistical analysis and bandpass filtering. The periods of wave processes were shown to be of 30 - 120 min, there durations did not exceed of 2 - 6 periods and relative amplitudes usually ranged from 0.03 to 0.15. The phase of oscillations was detected to propagate downwards. The vertical phase velocity of travelling ionospheric disturbances (TIDs) was estimated to be in the range from 50 to 200 m/s and increased with altitude. The observations of the partial solar eclipse on January, 4, 2011 near Kharkiv were used to study the ionospheric parameters in naturally disturbed conditions. The F2-layer critical frequency dropped by a factor of 2.1. The time delay of these variations with respect to the main magnitude of the solar disk obscuration was equal to about 16 minutes. The virtual height of signal reflection near the maximum of the F2-layer ionization increased by 70 km, and the height of the model parabolic layer increased by 10 km. Some decrease in electron density and

  19. [Effect of geomagnetic activity on the human body in extreme conditions and correlation with data from laboratory observations].

    PubMed

    Breus, T K; Baevskiĭ, R M; Nikulina, G A; Chibisov, S M; Chernikova, A G; Pukhlianko, M; Oraevskiĭ, V N; Halberg, F; Cornelissen, G; Petrov, V M

    1998-01-01

    It was hypothesized based on previous laboratory observations and theoretical concepts that astronauts working at the "Mir" station under zero gravity conditions exhibit enhanced sensitivity to geomagnetic disturbances. The result of studies made it possible to reveal the dynamics of changes in cardiovascular characteristics separately in the main phase and the phase of storm restoration. A similar dynamics of cardiac activity was observed in experimental rabbits during geomagnetic storms.

  20. Quiet-time electron increases, a measure of conditions in the outer solar system

    NASA Technical Reports Server (NTRS)

    Fisk, L. A.; Vanhollebeke, M.

    1972-01-01

    One possible explanation for quiet-time electron increases, increases in the intensity of 3-12 MeV interplanetary electrons that have been reported by McDonald, Cline and Simnett, is discussed. It is argued that the electrons in quiet-time increases are galactic in origin, but that the observed increases are not the result of any variation in the modulation of these particles in the inner solar system. It is suggested instead that quiet-time increases may occur when more electrons than normal penetrate a modulating region that lies far beyond the orbit of earth. The number of electrons penetrating this region may increase when field lines that have experienced an unusually large random walk in the photosphere are carried by the solar wind out to the region. As evidence for this increased random walk, it is shown that five solar rotations before most of the quiet-time increases there is an extended period when the amplitude of the diurnal anisotropy, as is measured by the Deep River neutron monitor, is relatively low. Five rotations delay time implies that the proposed modulating region lies at approximately 30 AU from the Sun, assuming that the average solar wind speed is constant over this distance at approximately 400 km/sec.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Records of geomagnetic activity have previously been used to reconstruct the conditions in near-Earth space, such as the interplanetary magnetic field (IMF), solar wind speed (Vsw) and open solar flux (OSF). Reliable geomagnetic activity records exist back until the mid-1800's, and these data provide one of the few means of inferring variations in the conditions in near-Earth space before the advent of the space age. However, there are challenges in using geomagnetic activity records to reconstruct interplanetary conditions. In particular it is necessary to ensure, as best as is possible, the homogeneity and reliability of any geomagnetic indices used. This becomes increasingly difficult further back in history, as both the quality of the data and the number of observing stations decreases. A new geomagnetic activity index, the IDV(1D) index, is presented, which is designed to be as homogeneous in its construction as possible (Lockwood et al. 2013a). This is achieved by only combining data that, by virtue of the locations of the source observatories used, have similar responses to solar wind and IMF variations. IDV(1d) employs many of the principles of the IDV index (Svalgaard and Cliver (2010)), inspired by the u index of Bartels (1932). The index uses interdiurnal variation data from Helsinki for 1845- 1890 and 1893-1896 and from Eskdalemuir from 1911 to the present. The gaps are filled using data from the Potsdam (1891-1892 and 1897-1907) and the nearby Seddin observatories (1908-1910) and intercalibration achieved using the Potsdam-Seddin sequence. The index is compared with independent, early data from European-sector stations, as well as the composite u index and the IDV index. Agreement is found to be extremely good in most cases. IDV(1D) does not suffer from the poor homogeneity of the IDV index, and is more highly correlated with the IMF, consequently it yields a more reliable reconstruction (Lockwood et al 2013b). For completeness, we use 4 different

  2. 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.

  3. 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

  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. On cosmic rays flux variations in midlatitudes and their relations to geomagnetic and atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Morozova, Anna; Blanco, Juan Jose; Mendes Ribeiro, Paulo Fernando

    The cosmic rays flux is globally modulated by the solar cycle and shows anti-correlation with the sunspot number. Near to the Earth it is modulated by the solar wind and the Earth's magnetic field. The analysis of the secondary cosmic rays produced when they interact in the low stratosphere allows extracting information about solar wind structures surrounding Earth's orbit, the magnetic field of the Earth and the temperature of the stratosphere. Recently, a new cosmic ray detector, the TRAGALDABAS, composed by RPC (Resistive Plate Chamber) planes, has been developed and installed to go deeper into the understanding of the cosmic rays arriving to the Earth surface. An international collaboration has been organized for keeping the detector operative and for analyzing the data. Here we present the analysis of the cosmic rays flux variations measured by two cosmic rays detectors of different types located in Spain (Castilla-La Mancha Neutron Monitor - CaLMa - in Guadalajara and TRAGALDABAS in Santiago de Compostela) and their comparison to changes both in the geomagnetic field components measured by the Coimbra Geomagnetic Observatory (Portugal) and in the atmospheric conditions (tropo- and stratosphere) measured by Spanish and Portuguese meteorological stations. The study is focused on a number of recent cosmic rays events and pays specific attention to the comparison of the CaLMa series and the preliminary TRAGALDABAS data.

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

    PubMed

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

    2014-04-01

    To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz  ≤ -5 nT or Ey  ≥ 3 mV/m for t≥ 2 h for moderate storms with minimum Dst less than -50 nT) and a Dst model developed by Temerin and Li (2002, 2006) (TL model). Using 55 CME-Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90%) than the forecasts based on the TL model (87%). However, the latter produces better forecasts for 24 nonstorm events (88%), while the former correctly forecasts only 71% of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80%) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (∩), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81%) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (∪), all geomagnetic storms are correctly forecasted.

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

    PubMed Central

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

    2014-01-01

    To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz ≤ −5 nT or Ey ≥ 3 mV/m for t≥ 2 h for moderate storms with minimum Dst less than −50 nT) and a Dst model developed by Temerin and Li (2002, 2006) (TL model). Using 55 CME-Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90%) than the forecasts based on the TL model (87%). However, the latter produces better forecasts for 24 nonstorm events (88%), while the former correctly forecasts only 71% of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80%) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (∩), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81%) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (∪), all geomagnetic storms are correctly forecasted. PMID:26213515

  8. Modelling total electron content during geomagnetic storm conditions using empirical orthogonal functions and neural networks

    NASA Astrophysics Data System (ADS)

    Uwamahoro, Jean Claude; Habarulema, John Bosco

    2015-12-01

    It has been shown in ionospheric research that modelling total electron content (TEC) during storm conditions is a big challenge. In this study, TEC modelling was performed over Sutherland (32.38°S, 20.81°E, 41.09°S geomagnetic), South Africa, during storm conditions, using a combination of empirical orthogonal function (EOF) and regression analyses techniques. The neural network (NN) technique was also applied to the same TEC data set, and its output was compared with TEC modeled using the EOF model. TEC was derived from GPS observations, and a geomagnetic storm was defined for Dst≤-50 nT. The hour of the day and the day number of the year, F10.7p and A indices, were chosen as inputs for the modeling techniques to take into account diurnal and seasonal variation of TEC, solar, and geomagnetic activities, respectively. Both EOF and NN models were developed using GPS TEC data for storm days counted from 1999 to 2013 and tested on different storms. For interpolation, the EOF and NN models were validated on storms that occurred during high and low solar activity periods (storms of 2000 and 2006), while for extrapolation the validation was done for the storms of 2014 and 2015, identified based on the provisional Dst index data. A comparison of the modeled TEC with the observed TEC showed that both EOF and NN models perform well for storms with nonsignificant ionospheric TEC response and storms that occurred during period of low solar activity. For storms with significant TEC response, TEC magnitude is well captured during the nighttime and early morning, but short-term features, TEC enhancement, and depression are not sufficiently captured by the models. Statistically, the NN model performs 12.79% better than the EOF model on average, over all storm periods considered. Furthermore, it has been shown that the EOF and NN models developed for a specific station can be used to estimate TEC over other locations within a latitudinal and longitudinal coverage of 8.7

  9. Intensive MHD-structures penetration in the middle atmosphere initiated in the ionospheric cusp under quiet geomagnetic conditions

    NASA Technical Reports Server (NTRS)

    Mateev, L. N.; Nenovski, P. I.; Vellinov, P. I.

    1989-01-01

    In connection with the recently detected quasiperiodical magnetic disturbances in the ionospheric cusp, the penetration of compressional surface magnetohydrodynamic (MHD) waves through the middle atmosphere is modelled numerically. For the COSPAR International Reference Atmosphere (CIRA) 72 model the respective energy density flux of the disturbances in the middle atmosphere is determined. On the basis of the developed model certain conclusions are reached about the height distribution of the structures (energy losses, currents, etc.) initiated by intensive magnetic cusp disturbances.

  10. Cosmic rays, conditions in interplanetary space and geomagnetic variations during solar cycles 19-24

    NASA Astrophysics Data System (ADS)

    Biktash, Lilia

    2016-07-01

    We have studied conditions in interplanetary space, which can have an influence on galactic and solar cosmic rays (CRs). In this connection the solar wind and interplanetary magnetic field parameters and CRs variations have been compared with geomagnetic activity represented by the equatorial Dst and Kp indices beginning from 1955 to the end 2015. The indices are in common practice in the solar wind-magnetosphere-ionosphere interaction studies and they are the final product of this interaction. The important drivers in interplanetary medium which have effect on cosmic rays as CMEs (coronal mass ejections) and CIRs (corotating interaction regions) undergo very strong changes during their propagation to the Earth. Correlation of sunspot numbers and long-term variations of cosmic rays do not adequately reflect peculiarities concerned with the solar wind arrival to 1 AU also. Moreover records of in situ space measurements of the IMF and most other indicators of solar activity cover only a few decades and have a lot of gaps for calculations of long-term variations. Because of this, in such investigations, the geomagnetic indices have some inestimable advantage as continuous series other the solar wind measurements. We have compared the yearly average variations of the indices and of the solar wind parameters with cosmic ray data from Moscow, Climax, Halekala and Oulu neutron monitors during the 20-24 solar cycles. During the descending phases of the solar cycles the long-lasting solar wind high speed streams occurred frequently and were the primary contributors to the recurrent Dst variations and had effects on cosmic rays variations. We show that long-term Dst and Kp variations in these solar cycles were correlated with cosmic ray count rates and can be used for prediction of CR variations. Climate change in connection with evolution of CRs variations is discussed.

  11. 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

  12. Geomagnetic disturbances effects on earths environ and relationship to interplanetary conditions

    NASA Astrophysics Data System (ADS)

    Okeke, F. N.; Hanson, E. A.; Okoro, E. C.

    2009-12-01

    Dynamic processes in the sun deliver plasma of charged particles and associated fields to the earth’s environments, causing geomagnetic disturbances at the earth’s surface. This study has enabled us to ascertain that; during geomagnetic disturbances, coronal mass ejection (CME) play dominant role and triggers most interplanetary disturbances. Hence, solar wind streams are invariably affected, and equatorial electrojet (EEJ) is found to increase the storm time index (Dst) variation. On the other hand, counter electrojet (CEJ) favours reduction in Dst variation. It was equally discovered that formation of CEJ could be attributed to interplanetary magnetic field (IMF). It was then concluded that the geomagnetic disturbance phenomena is latitude dependent.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  14. 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

  15. 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.

  16. Effects of orbit progression on the radiation exposures from solar proton fluxes in low Earth orbit under geomagnetic storm conditions

    NASA Technical Reports Server (NTRS)

    Nealy, J. E.; Wilson, J. W.; Shea, M. A.; Smart, D. F.

    1996-01-01

    The present study examines the effects of orbit progression on the exposures within a Space Station Freedom module in a 51.6-degree inclined orbit at 450 km. The storm evolution is modeled after the November 1960 event, and the solar proton flux evolution is taken from the August 1972 solar proton event. The effects of a strong magnetic shock, such as was observed during the October 1989 event, is also modeled. The statistics on hourly average storm fields for the last forty years reveal that the largest geomagnetic storms geomagnetic storms approach a Dst value of -500 nanotesla at the storm peak. Similarly, one of the largest satellite-measured proton flux (greater than 10 MeV) for space exposures is the event of August 1972. The effects of orbit progression (advance of the line of nodes) is examined for the above conditions to study the variation of exposures under differing times of occurrence of the solar proton peak intensity, attainment of geomagnetic storm maximum, and the location of the line of nodes of the last geomagnetically protected orbit. The impact of the inherent inhomogeneity of the space station module is examined as a limiting factor on exposure with regard to the need of additional parasitic shielding.

  17. Long-period irregular pulsations under the conditions of a quiet magnetosphere

    NASA Astrophysics Data System (ADS)

    Kurazhkovskaya, N. A.; Klain, B. I.; Lavrov, I. P.

    2016-05-01

    Simultaneous observations of high-latitude long-period irregular pulsations at frequencies of 2.0-6.0 mHz ( ipcl) and magnetic field disturbances in the solar wind plasma at low geomagnetic activity ( Kp ~ 0) have been studied. The 1-s data on the magnetic field registration at Godhavn (GDH) high-latitude observatory and the 1-min data on the solar wind plasma and IMF parameters for 2011-2013 were used in an analysis. Ipcl (irregular pulsations continuous, long), which were observed against a background of the IMF Bz reorientation from northward to southward, have been analyzed. In this case other solar wind plasma and IMF parameters, such as velocity V, density n, solar wind dynamic pressure P = ρ V 2 (ρ is plasma density), and strength magnitude B, were relatively stable. The effect of the IMF Bz variation rate on the ipcl spectral composition and intensity has been studied. It was established that the ipcl spectral density reaches its maximum (~10-20 min) after IMF Bz sign reversal in a predominant number of cases. It was detected that the ipcl average frequency ( f) is linearly related to the IMF Bz variation rate (Δ Bz/Δ t). It was shown that the dependence of f on Δ Bz/Δ t is controlled by the α = arctan( By/ Bx) angle value responsible for the MHD discontinuity type at the front boundary of magnetosphere. The results made it possible to assume that the formation of the observed ipcl spectrum, which is related to the IMF Bz reorientation, is caused by solar wind plasma turbulence, which promotes the development of current sheet instability and surface wave amplification at the magnetopause.

  18. The role of high-resolution geomagnetic field models for investigating ionospheric currents at low Earth orbit satellites

    NASA Astrophysics Data System (ADS)

    Stolle, Claudia; Michaelis, Ingo; Rauberg, Jan

    2016-07-01

    Low Earth orbiting geomagnetic satellite missions, such as the Swarm satellite mission, are the only means to monitor and investigate ionospheric currents on a global scale and to make in situ measurements of F region currents. High-precision geomagnetic satellite missions are also able to detect ionospheric currents during quiet-time geomagnetic conditions that only have few nanotesla amplitudes in the magnetic field. An efficient method to isolate the ionospheric signals from satellite magnetic field measurements has been the use of residuals between the observations and predictions from empirical geomagnetic models for other geomagnetic sources, such as the core and lithospheric field or signals from the quiet-time magnetospheric currents. This study aims at highlighting the importance of high-resolution magnetic field models that are able to predict the lithospheric field and that consider the quiet-time magnetosphere for reliably isolating signatures from ionospheric currents during geomagnetically quiet times. The effects on the detection of ionospheric currents arising from neglecting the lithospheric and magnetospheric sources are discussed on the example of four Swarm orbits during very quiet times. The respective orbits show a broad range of typical scenarios, such as strong and weak ionospheric signal (during day- and nighttime, respectively) superimposed over strong and weak lithospheric signals. If predictions from the lithosphere or magnetosphere are not properly considered, the amplitude of the ionospheric currents, such as the midlatitude Sq currents or the equatorial electrojet (EEJ), is modulated by 10-15 % in the examples shown. An analysis from several orbits above the African sector, where the lithospheric field is significant, showed that the peak value of the signatures of the EEJ is in error by 5 % in average when lithospheric contributions are not considered, which is in the range of uncertainties of present empirical models of the EEJ.

  19. How Quiet is the Quiet Magnetosphere?

    NASA Astrophysics Data System (ADS)

    Hesse, M.; Moretto, T.; Friis-Christensen, E. A.; Opgenoorth, H. J.

    2015-12-01

    The term "quiet magnetosphere" has been accepted as a descriptor of a magnetospheric state under small solar wind driving conditions. Observations indicate that such a state entails a substantial reduction of field-aligned currents, the polar cap potential, polar cap size, and general convection in the magnetosphere. While this paradigm is often discussed, little research has been applied to determine the detailed state of the structure of the magnetosphere. Due to basic constraints, such as entropy conservation, it appears, for example, very likely that the state of the quiet magnetosphere depends on the dynamic history. Relaxation to a unique relaxed state, should, if at all, only be possible on some yet undetermined relaxation time scale. Finally, the quiet state should depend on residual fluctuations in the solar wind driver, even if the IMF is northward. This presentation is shedding some first light on the issue of the quiet magnetosphere. We are using global MHD simulations to study the relaxation process starting from different driven states. By studying different key parameters, we derive estimates for relaxation time scales, and we will demonstrate the role solar wind fluctuations play in shaping the typical behavior of a relaxed magnetosphere.

  20. Quiet Ride

    ERIC Educational Resources Information Center

    Rathey, Allen

    2006-01-01

    Several companies are marketing maintenance equipment to education institutions on a "quiet platform," citing benefits such as a safer, more pleasant indoor environment and unobtrusive operations during day cleaning or operating hours. This is basically "sound advice" (no one likes noisy equipment), but some of the messages can be confusing and…

  1. The geomagnetic control of the lower thermosphere wind system over East Siberia

    NASA Technical Reports Server (NTRS)

    Kazimirovsky, E. S.; Gergasova, G. V.; Zhovty, E. I.; Chernigovskaya, M. A.

    1989-01-01

    The geomagnetic control of ionospheric D region dynamics was revealed and confirmed on the basis of radiophysical wind measurements (1978 to 1983) over East Siberia. The monthly mean parameters of the wind system are different for quiet and disturbed conditions. There is an increase in stability of the meridional wind with increasing level of geomagnetic activity. The influence of geomagnetic storms on the measured wind is considered on the basis of 31 events. There are effects on the phase of the semidiurnal tidal wind, but variations of amplitude are weak. The effect of the geomagnetic storm depends on the intensity and is more clear-cut for the A sub p is greater than 100.

  2. 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

  3. Ionospheric data assimilation with thermosphere-ionosphere-electrodynamics general circulation model and GPS-TEC during geomagnetic storm conditions

    NASA Astrophysics Data System (ADS)

    Chen, C. H.; Lin, C. H.; Matsuo, T.; Chen, W. H.; Lee, I. T.; Liu, J. Y.; Lin, J. T.; Hsu, C. T.

    2016-06-01

    The main purpose of this paper is to investigate the effects of rapid assimilation-forecast cycling on the performance of ionospheric data assimilation during geomagnetic storm conditions. An ensemble Kalman filter software developed by the National Center for Atmospheric Research (NCAR), called Data Assimilation Research Testbed, is applied to assimilate ground-based GPS total electron content (TEC) observations into a theoretical numerical model of the thermosphere and ionosphere (NCAR thermosphere-ionosphere-electrodynamics general circulation model) during the 26 September 2011 geomagnetic storm period. Effects of various assimilation-forecast cycle lengths: 60, 30, and 10 min on the ionospheric forecast are examined by using the global root-mean-squared observation-minus-forecast (OmF) TEC residuals. Substantial reduction in the global OmF for the 10 min assimilation-forecast cycling suggests that a rapid cycling ionospheric data assimilation system can greatly improve the quality of the model forecast during geomagnetic storm conditions. Furthermore, updating the thermospheric state variables in the coupled thermosphere-ionosphere forecast model in the assimilation step is an important factor in improving the trajectory of model forecasting. The shorter assimilation-forecast cycling (10 min in this paper) helps to restrain unrealistic model error growth during the forecast step due to the imbalance among model state variables resulting from an inadequate state update, which in turn leads to a greater forecast accuracy.

  4. Modeling the Quiet Time Outflow Solution in the Polar Cap

    NASA Technical Reports Server (NTRS)

    Glocer, Alex

    2011-01-01

    We use the Polar Wind Outflow Model (PWOM) to study the geomagnetically quiet conditions in the polar cap during solar maximum, The PWOM solves the gyrotropic transport equations for O(+), H(+), and He(+) along several magnetic field lines in the polar region in order to reconstruct the full 3D solution. We directly compare our simulation results to the data based empirical model of Kitamura et al. [2011] of electron density, which is based on 63 months of Akebono satellite observations. The modeled ion and electron temperatures are also compared with a statistical compilation of quiet time data obtained by the EISCAT Svalbard Radar (ESR) and Intercosmos Satellites (Kitamura et al. [2011]). The data and model agree reasonably well. This study shows that photoelectrons play an important role in explaining the differences between sunlit and dark results, ion composition, as well as ion and electron temperatures of the quiet time polar wind solution. Moreover, these results provide validation of the PWOM's ability to model the quiet time ((background" solution.

  5. Substorm occurrence during quiet solar wind driving

    NASA Astrophysics Data System (ADS)

    Pulkkinen, T. I.; Partamies, N.; Kilpua, E. K. J.

    2014-04-01

    We examine the OMNI database and International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer chain records to study the substorm occurrence and characteristics during quiet solar driving periods, especially during the solar minimum period in 2009. We define substorm-like activations as periods where the hourly average AL is below -200 nT. Using the OMNI data set, we demonstrate that there are limiting solar wind speed, interplanetary magnetic field magnitude, and driving electric field values below which substorm-like activations (AL < 200 nT, intensification and decay of the electrojet) do not occur. These minimum parameter values are V < 266 km/s, B < 1.4 nT, and E < 0.025 mV/m such low values are observed less than 1% of the time. We also show that for the same level of driving solar wind electric field, the electrojet intensity is smaller (by few tens of nT), and the electrojet resides farther poleward (by over 1°) during extended quiet solar driving in 2009 than during average solar activity conditions. During the solar minimum period in 2009, we demonstrate that substorm-like activations can be identified from the IMAGE magnetometer chain observations during periods when the hourly average IL index is below -100 nT. When the hourly IL activity is smaller than that, which covers 87% of the nighttime observations, the electrojet does not show coherent behavior. We thus conclude that substorm recurrence time during very quiet solar wind driving conditions is about 5-8 h, which is almost double that of the average solar activity conditions.

  6. Stochastic properties of the geomagnetic field across the 210 mm chain

    NASA Astrophysics Data System (ADS)

    Wanliss, J. A.; Shiokawa, K.; Yumoto, K.

    2013-12-01

    We explore the stochastic fractal qualities of the geomagnetic field from 210 mm ground-based magnetometers during quiet and active magnetospheric conditions. We search through 10 years of these data to find events that qualify. Quiet intervals are defined by Kp ≤ 1 for 1,440 consecutive minutes. Similarly, active intervals require Kp ≥ 4 for 1,440 consecutive minutes. The total for quiet intervals is ~4.3×106 minutes and 2×108 minutes for active data points. With this large number of events compiled we then characterize changes in the nonlinear statistics of the geomagnetic field via measurements of a fractal scaling exponent. A clear difference in statistical behavior during quiet and active intervals is implied through analysis of the scaling exponents; active intervals generally have larger values of scaling exponents. This means that although 210 mm data appears monofractal on shorter timescales, it is more properly described as a multifractional Brownian motion. Long-range statistical behavior of the geomagnetic field at a local observation site can be described as a multifractional Brownian motion, thus suggesting the statistical structure required of mathematical models of magnetospheric activity. We also find that low-latitudes have scaling exponents that are consistently larger than for high-latitudes.

  7. Effects of orbit progression on the radiation exposures from solar proton fluxes in low Earth orbit under geomagnetic storm conditions.

    PubMed

    Nealy, J E; Wilson, J W; Shea, M A; Smart, D F

    1996-01-01

    The present study examines the effects of orbit progression on the exposures within a Space Station Freedom module in a 51.6-degree inclined orbit at 450 km. The storm evolution is modeled after the November 1960 event, and the solar proton flux evolution is taken from the August 1972 solar proton event. The effects of a strong magnetic shock, such as was observed during the October 1989 event, is also modeled. The statistics on hourly average storm fields for the last forty years reveal that the largest geomagnetic storms approach a Dst value of -500 nanotesla at the storm peak. Similarly, one of the largest satellite-measured proton flux (> 10 MeV) for space exposures is the event of August 1972. The effects of orbit progression (advance of the line of nodes) is examined for the above conditions to study the variation of exposures under differing times of occurrence of the solar proton peak intensity, attainment of geomagnetic storm maximum, and the location of the line of nodes of the last geomagnetically protected orbit. The impact of the inherent inhomogeneity of the space station module is examined as a limiting factor on exposure with regard to the need of additional parasitic shielding.

  8. Latitudinal variation of 732.0 nm dayglow emission under geomagnetic storm conditions

    NASA Astrophysics Data System (ADS)

    Singh, Vir; Dharwan, Maneesha

    2016-07-01

    A comprehensive model is developed to study 732.0 nm dayglow emission. The Solar2000 EUV (extreme ultraviolet) flux model, neutral atmosphere model (NRLMSISE-00), latest transition probabilities and updated reaction rate coefficients are incorporated in the present model. The modeled volume emission rates (VER) are compared with the measurements as provided by Atmosphere Explorer-C satellite, Dynamics Explorer-2 spacecraft and WINDII measurements. The model is found in very good agreement with the measurements. This model is used to study the effects of geomagnetic storm on the 732.0 nm dayglow emission at various latitudes in northern hemisphere. It is found that the VER decreases as the latitude increases. The decrease in VER from low to mid latitudes is due to the decrease in atomic oxygen number density with latitude. The zenith intensity at the maximum geomagnetic activity is about 15% higher than the zenith intensity before the start of the geomagnetic storm in equatorial region. However, no appreciable change in the zenith intensity is found at higher latitudes (above 50° N). Further a negative correlation is found between the volume emission rate and DST index at all latitudes.

  9. Contributions from geomagnetic inverse theory to the study of hydromagnetic conditions near the core-mantle boundary

    NASA Technical Reports Server (NTRS)

    Backus, George E.

    1991-01-01

    The Final Report on contributions from geomagnetic inverse theory to the study of hydromagnetic conditions near the core-mantle boundary (CMB) is presented. The original proposal was to study five questions concerning what the surface and satellite magnetic data imply about hydromagnetic and electromagnetic conditions near the CMB. The five questions are: (1) what do the surface and satellite data imply about the geomagnetic field B near the surface of the earth; (2) how does one extrapolate B down through the conducting mantle to the CMB; (3) if B on the CMB is visible, how accurately does it satisfy the frozen-flux approximation; (4) if frozen flux is a good approximation on the CMB, what can be inferred about the fluid velocity v in the upper core; and (5) if v at the CMB is visible, does it suggest any dynamical properties of the core, such as vertical advection, Alfven-inertial waves, link instabilities, or mantle effects. A summary of the research is provided.

  10. 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.

  11. Behaviour of the F2 peak ionosphere over Nicosia during quiet and disturb conditions from new DPS-4D ionosonde data

    NASA Astrophysics Data System (ADS)

    Cander, L.; Haralambous, H.

    2009-04-01

    Ionospheric specification data from digisonde ionograms are expected to become the important contributing technique for not only real-time propagation predictions but space weather applications as well. The new ionosonde has been making routine ionospheric measurements over Nicosia station (35 N, 33 E) since September 2008. These observations have been used to study the behaviour of the F2 peak for the duration of some specified quiet and disturb periods in equinox and winter ionosphere at very low solar activity. In particular, enhanced electron densities that appear to be associated with the 11 October 2008 event, when the arrival of a fast solar wind stream from a coronal hole produced a geomagnetic storm (Kp reached 7), suggesting that the electron density increases are connected with the F 2 peak rising. As well as being an interesting phenomenon in its own right, this behaviour may shed new light on the formation of the ionospheric evening anomaly. No unambiguous explanation for this behaviour can be determined from the data presently available, but an examination of some possibilities suggests that an evening downward flux of plasma from the plasmasphere may be at least partly responsible for the phenomenon. While the main purpose of this paper is to inform the users of digisondes and of digisonde data about the new ionospheric station operating at Nicosia, some of the ideas here presented may be of use to other algorithm developers for single station physics-based modelling.

  12. Solar Cyclical Trend Study of the Mid-Latitude, Quiet-Time, Meridional, Neutral Winds at Winter Solstice Conditions

    DTIC Science & Technology

    1989-01-01

    thermospheric heights [Rishbeth, 1972]. Thermospheric winds blow from the hottest part of the thermosphere to the coldest part and therefore blow across the...19 2. Description of Ionosonde Stations ..... 66 3. Geomagnetic and Solar Data ............ .67 V LIST OF FIGURES Figure Page 1. Vertical temperature ...1977]. . . . . . .................... 12 4. Contour of temperature and winds for winter solstice at solar minimum; (a) meridional winds (m/s), (b) zonal

  13. Performance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Abe, O. E.; Otero Villamide, X.; Paparini, C.; Radicella, S. M.; Nava, B.; Rodríguez-Bouza, M.

    2017-04-01

    Global Navigation Satellite Systems (GNSS) have become a powerful tool use in surveying and mapping, air and maritime navigation, ionospheric/space weather research and other applications. However, in some cases, its maximum efficiency could not be attained due to some uncorrelated errors associated with the system measurements, which is caused mainly by the dispersive nature of the ionosphere. Ionosphere has been represented using the total number of electrons along the signal path at a particular height known as Total Electron Content (TEC). However, there are many methods to estimate TEC but the outputs are not uniform, which could be due to the peculiarity in characterizing the biases inside the observables (measurements), and sometimes could be associated to the influence of mapping function. The errors in TEC estimation could lead to wrong conclusion and this could be more critical in case of safety-of-life application. This work investigated the performance of Ciraolo's and Gopi's GNSS-TEC calibration techniques, during 5 geomagnetic quiet and disturbed conditions in the month of October 2013, at the grid points located in low and middle latitudes. The data used are obtained from the GNSS ground-based receivers located at Borriana in Spain (40°N, 0°E; mid latitude) and Accra in Ghana (5.50°N, 0.20°E; low latitude). The results of the calibrated TEC are compared with the TEC obtained from European Geostationary Navigation Overlay System Processing Set (EGNOS PS) TEC algorithm, which is considered as a reference data. The TEC derived from Global Ionospheric Maps (GIM) through International GNSS service (IGS) was also examined at the same grid points. The results obtained in this work showed that Ciraolo's calibration technique (a calibration technique based on carrier-phase measurements only) estimates TEC better at middle latitude in comparison to Gopi's technique (a calibration technique based on code and carrier-phase measurements). At the same time

  14. Performance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Abe, O. E.; Otero Villamide, X.; Paparini, C.; Radicella, S. M.; Nava, B.; Rodríguez-Bouza, M.

    2016-11-01

    Global Navigation Satellite Systems (GNSS) have become a powerful tool use in surveying and mapping, air and maritime navigation, ionospheric/space weather research and other applications. However, in some cases, its maximum efficiency could not be attained due to some uncorrelated errors associated with the system measurements, which is caused mainly by the dispersive nature of the ionosphere. Ionosphere has been represented using the total number of electrons along the signal path at a particular height known as Total Electron Content (TEC). However, there are many methods to estimate TEC but the outputs are not uniform, which could be due to the peculiarity in characterizing the biases inside the observables (measurements), and sometimes could be associated to the influence of mapping function. The errors in TEC estimation could lead to wrong conclusion and this could be more critical in case of safety-of-life application. This work investigated the performance of Ciraolo's and Gopi's GNSS-TEC calibration techniques, during 5 geomagnetic quiet and disturbed conditions in the month of October 2013, at the grid points located in low and middle latitudes. The data used are obtained from the GNSS ground-based receivers located at Borriana in Spain (40° N, 0° E; mid latitude) and Accra in Ghana (5.50° N, -0.20° E; low latitude). The results of the calibrated TEC are compared with the TEC obtained from European Geostationary Navigation Overlay System Processing Set (EGNOS PS) TEC algorithm, which is considered as a reference data. The TEC derived from Global Ionospheric Maps (GIM) through International GNSS service (IGS) was also examined at the same grid points. The results obtained in this work showed that Ciraolo's calibration technique (a calibration technique based on carrier-phase measurements only) estimates TEC better at middle latitude in comparison to Gopi's technique (a calibration technique based on code and carrier-phase measurements). At the same

  15. 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.

  16. Pre-Cretaceous Tectonic Evolution of the Pacific Plate and Extension of the Geomagnetic Polarity Reversal Time Scale with Implications for the Origin of the Jurassic ’Quiet Zone’

    DTIC Science & Technology

    1987-03-01

    decreasing geomagnetic field strength with increasing age during this period. The early history of the northern Pacific plate and Pacific- Farallon -lzanagi...scale. A number of the Pacific, Farallon and Izanagi plates (Hilde et workers measured magnetic lineations in the west- al., 1976; Woods and Davies, 1982...formed at a RRR triple junction between the over, many models of the geometry of the polarity Phoenix, Farallon and Izanagi plates at 180 Ma blocks within

  17. First observations of poleward large-scale traveling ionospheric disturbances over the African sector during geomagnetic storm conditions

    NASA Astrophysics Data System (ADS)

    Habarulema, John Bosco; Katamzi, Zama Thobeka; Yizengaw, Endawoke

    2015-08-01

    This paper presents first observations of poleward traveling ionospheric disturbances (TIDs) during strong geomagnetic conditions over the African sector. By analyzing different data sets we have observed both positive and negative ionospheric responses during the storm period of 08-10 March 2012. Considering the African region as a whole, three longitudinal sectors were strategically selected to establish the entire regional response. On both sides of the geomagnetic equator, results show poleward shift in peak total electron content (TEC) enhancements/depletions at different times which are associated to large-scale TIDs. The observed phenomena are linked to the global ionospheric response and electrodynamics. The understanding has been established using data from International GNSS Service receiver network, radio occultation electron density profiles, derived E×B drift measurements from magnetometer observations and regional ground-based and satellite data. Contrary to other related studies, generated regional TEC perturbation maps were not enough to show obvious directions of the large-scale TIDs due to insufficient data over the northern hemispheric part of the African sector. There appears to be a switch between positive and negative storm phases during the same storm period especially in the Southern Hemisphere part of the African region where "enough" data were available. However, a detailed analysis revealed that the positive storm phase corresponded to the expansion of the equatorial ionization anomaly (EIA) toward some parts of midlatitude regions (and possibly with the contribution from low-latitude electrodynamics associated to equatorial electrojet), while the other part recorded a negative storm phase due to storm-induced changes from the auroral origin. We have observed a simultaneous occurrence of both poleward and equatorward propagating TIDs over the African sector during the same geomagnetic storm period. Our results show that short-lived large

  18. Geomagnetic activity effects on semidiurnal winds in the lower thermosphere

    NASA Astrophysics Data System (ADS)

    Wand, R. H.

    1983-11-01

    Steerable (L band) and fixed (UHF) radars were used in observing the incoherent scatter of E and F region ion drifts between July 1976 and November 1977. The wind measurements typically exhibited strong 12-hour oscillations with the eastward wind component reaching a maximum three hours ahead of the southward wind component. The results are seen as implying that the neutral winds are being dominated by semidiurnal tides. The geomagnetic activity dependence of the semidiurnal winds is arrived at by dividing the observations into quiet and disturbed periods on the basis of the Kp index. The winds during disturbed conditions were found to be significantly altered from the quiet time behavior, with the semidiurnal amplitudes reduced by 20 to 50 percent at the lowest altitudes and the altitude of maximum wind increased to be above 125 km. Under disturbed conditions, a decrease is also seen in the vertical wavelength. It is thought that some of these effects might derive from geomagnetic-activity induced changes in lower thermospheric temperature and density, which alter the dissipation of the upward-propagating tidal component.

  19. 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.

  20. Pulsed HF radiowave absorption measurements at 2.1 MHZ. over Delhi under quiet and solar flare conditions and related electron density height profiles

    NASA Astrophysics Data System (ADS)

    Balachandra Swamy, A. C.

    EXTENDED ABSTRACT Pulsed HF radiowave absorption measurements at 2.1 MHZ. over Delhi under quiet and solar flare conditions and related electron density height profiles A.C.Balachandra swmay & Late C.S.G.K. Setty Absorption of radio waves in the ionosphere is of great practical importance for radio communication and navigation systems. The first attempt to measure the absolute magnitude of the radiowave absorption were made by appletion and Ratcliffe (1930) using the frequency change method for medium frequency waves reflected from the E-region. They concluded from their experiment that the main part of the attenuation occurred below the reflection level and named the absorption region, D-region of the ionosphere. One of the basic properties of the ionosphere is the absorption of high Frequency Radiowaves. HF radiowave absorption results mainly from collisions between electrons (which are set into forced oscillations by the electric field of the wave) and neutral air particles, the RF energy abstracted from the wave being converted into thermal energy. The radiowave absorption in the ionosphere depends on electron density and collision frequency. The most important absorbing regions are the D-region and the lower E-region (50-100 Km.) The regular diurnal variation of the electron density in this height range is caused mainly by the changes in the depth of penetration of solar XUV radiations with solar zenith angle under quiet solar conditions. In 1937 Dellinger J.H.identified fade outs in high frequency radio circuits as due to abnormal ionospheric absorption associated with solar flares. The onset of the fade out was usually rapid and the duration was typically tens of minutes like that of the visible flare, because of the sudden onset, the immediate effects of solar flares are known collectively as sudden Ionospheric Disturbances (STD). The phenomenon discovered by Dellinger is usually called a short Wave Fadeout(SWF). Since the SWF is due to abnormal absorption

  1. Investigation of Geomagnetic Storm Impact on Hourly PPP Static Coordinates

    NASA Astrophysics Data System (ADS)

    Öǧütcü, Sermet; Kalaycı, İbrahim

    2017-04-01

    This paper investigates the effect of geomagnetic storm on hourly Precise Point Positioning (PPP) static coordinates of IGS stations at mid-latitudes. 12 IGS stations in mid-latitude were chosen to conduct the experiment. These IGS stations were classified as non-cross correlation receiver reporting P1 and P2 (NONCC-P1P2), non-cross correlation receiver reporting C1 and P2 (NONCC-C1P2) and cross-correlation (CC-C1P2) receiver. Two extreme geomagnetic storms (October 29, 2003 Halloween Storm and November 20, 2003) and two geomagnetic quiet days in 2005 (DOY 98, 99) were chosen for this study. The processing was performed by GIPSY/OASIS 6.4 scientific software. After processing, root mean square errors (rms) of north, east and up component were calculated for each station and each day. In parallel, we generate vertical total electron content (VTEC) with 15 second interval for each station to detect small changes in VTEC and ionospheric scintillation during geomagnetic storm. The results indicate that three-dimensional (3D) accuracy of hourly PPP obtained during the geomagnetic storm for CC-P1P2 type of receiver is significantly low comparing the geomagnetic quiet days. When it comes to rms there is no statistically difference was observed between the geomagnetic quiet days and geomagnetic disturbed days for all NONCC-C1P2 and NONCC-C1P2 receivers. As far as outliers are concern, significant increase was observed for the geomagnetic disturbed days comparing with the geomagnetic quiet days.

  2. 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.

  3. 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.

  4. Inter-hourly variability of Total Electron Content during the quiet condition over Nigeria, within the Equatorial Ionization Anomaly region

    NASA Astrophysics Data System (ADS)

    Ayorinde, T. T.; Rabiu, A. B.; Amory-Mazaudier, C.

    2016-07-01

    The inter-hourly variability (IHV) of the Total Electron Content (TEC) over Nigeria during the quiet days (Ap<4) of the year 2013 was examined using ground-based GPS receivers installed at seven (7) different locations across Nigeria by the Nigerian Global Navigation Satellite Systems (GNSS) Reference Network (NIGNET) operated by the office of the surveyor general of Nigeria. Nigeria is a country that lies within Equatorial Ionospheric Anomaly (EIA) region. The IHV was calculated by converting the observed hourly slant TEC (STEC) value into the hourly vertical TEC (VTEC) and the differencing (∆TEC) with its corresponding hourly value from the previous day. There is a clear variation which depicts the expected temporal variability. The IHV in TEC in all the stations ranges between 0 and 20 TECU (TEC Units). The seasonal variation of the IHV of TEC over Nigeria maximizes (5-20 TECU) during Equinoctial months and minimizes (1-10 TECU) during the Solstice months. The IHV of TEC in September equinox period is higher than that of March equinox. Minimum value of IHV (~7 TECU at equinoxes and ~5 TECU at Solstice) was recorded at the Office of Surveyor General of the Federation (OSGF) station and the maximum value (~12 TECU at equinoxes and ~16 TECU at Solstice) was recorded at the Birni Kebbi Federal Polytechnic (BKFP) station which may be due to the fact that BKFP at 0.72° dip latitude is closer to the dip equator.

  5. 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.

  6. Do somatosensory conditions from the foot and ankle affect postural responses to plantar-flexor muscles fatigue during bipedal quiet stance?

    PubMed

    Hlavackova, Petra; Vuillerme, Nicolas

    2012-05-01

    The present study investigated the effects of somatosensory conditions at the foot and ankle on postural responses to plantar-flexor muscle fatigue during bipedal quiet stance. Twenty-two young healthy adults were asked to stand upright as still as possible with their eyes closed in three somatosensory conditions (normal, altered and improved) both prior to and after exercises inducing plantar-flexor muscle fatigue. In the normal condition, the postural task was executed on a firm support surface constituted by the force platform. In the altered condition, a 2-cm thick foam support surface was placed under the subjects' feet. In the improved condition, increased cutaneous feedback at the foot and ankle was provided by strips of athletic tape applied across both their ankle joints. Muscle fatigue was induced in the plantar-flexor muscles of both legs through the execution of a repeated standing heel raise exercise. Centre of foot pressure displacements were recorded using a force platform. Results showed that plantar-flexor muscle fatigue yielded increased centre of foot pressure displacements under normal foot and ankle sensory conditions. Furthermore, this effect was exacerbated under altered foot and ankle sensory conditions and mitigated under improved foot and ankle sensory conditions. Altogether, the present findings suggested an increased reliance on somatosensory information from the foot and ankle for controlling upright posture in the presence of plantar-flexor muscle fatigue.

  7. The interplanetary magnetic field B sub y -dependent field-aligned current in the dayside polar cap under quiet conditions

    SciTech Connect

    Yamauchi, M. Kyoto Univ. ); Araki, T. )

    1989-03-01

    Spatial distribution and temporal variation of the interplanetary magnetic field (IMF) B{sub y}-dependent cusp region field-aligned currents (FACs) during quiet periods were studied by use of magnetic data observed by Magsat. The analysis was made for 11 events (each event lasts more than one and a half days) when the IMF B{sub y} component was steadily large and B{sub x} was relatively small ({vert bar}B{sub z}{vert bar} < {vert bar}B{sub y}{vert bar}). Results of the analysis of total 62 half-day periods for the IMF B{sub y}-dependent cusp region FAC are summarized as follows: (1) the IMF B{sub y}-dependent cusp region FAC is located at around 86{degree}-87{degree} invariant latitude local noon, which is more poleward than the location of the IMF B{sub z}-dependent cusp region FAC; (2) the current density of this FAC is greater than previous studies ({ge} 4 {mu}A/m{sup 2} for IMF B{sub y} = 6 nT); (3) there are two time scales for the IMF B{sub y}-dependent cusp region FAC to appear: the initial rise of the current is on a short time scale, {approximately} 10 min, and it is followed by a gradual increase on a time scale of several hours to a half day; (4) the seasonal change of this FAC is greater than that of the nightside region 1 or region 2 FACs; (5) the IMF B{sub z}-dependent cusp region FAC is not well observed around the cusp when the IMF B{sub y}-dependent cusp region FAC is intense.

  8. GEOS 1 observations of low-energy ions in the earth's plasmasphere - A study on composition, and temperature and density structure under quiet geomagnetic conditions

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Geiss, J.; Balsiger, H.; Young, D. T.

    Data are presented on the composition and the temperature (T) and density (N) distributions of the earth's plasmasphere ionic population, obtained from GEOS 1 thermal-ion data. In deriving the N and T of the ions, a novel technique was employed, which is based on the modulation of the count rates by the spacecraft's spin. It was found that, for the major ion species H(+) and He(+), the relative density abundance He(+)/H(+) value of several percent was fairly common; the H(+) and He(+) ions are generally in thermal equilibrium, with temperatures varying between 4000 and 15,000 K, with a tendency to increase with L value. A comparison of the thermal structure obtained with those obtained by the Plasma Composition Experiment on ISEE and the Retarding Ion Mass Spectrometer on DE 1 showed no systematic difference between the 'energy' techniques used in these studies and the present 'angular' technique.

  9. Geomagnetic Disturbances.

    DTIC Science & Technology

    1986-01-01

    Sheeley, Jr., and J.T. Hoeksema. Lund University, Lund , Sweden, August 1983 (Invited Talks): "The Structure of the Heliospheric Current Sheet: 1976...Society, San Franciso, California, January 13-16, 1980: "Geomagnetic Activity and Hale Sector Boundaries," Henrik Lundstedt. "Solar Oscillations with

  10. Effects of geomagnetic activity in the winter thermosphere 1. Magnetically undisturbed conditions

    SciTech Connect

    Hagan, M.E.; Salah, J.E. )

    1988-09-01

    A two-part study of the influence of magnetic variability on the structure and dynamics of the winter thermosphere as observed by incoherent scatter radars has been conducted. Here, in paper 1, the authors present a thermospheric case study for magnetically undisturbed geophysical conditions, which is used as a reference in studying the magnetic storm effects in paper 2. Neutral exospheric temperatures derived from incoherent scatter radar measurements made at Millstone Hill (43{degree}N), Arecibo (18{degree}N), and Sondrestrom (67{degree}N) between January 14 and 17, 1986, serve as the control case. Mean temperatures and diurnal temperature variations resulting from Fourier decomposition of these data are compared with the predictions of the MSIS-86 model and recent theoretical calculations. These comparisons confirm the largely reliable predictive capabilities of the magnetically undisturbed winter thermosphere models, but point to some inconsistencies in the horizontal structure of diurnal temperature amplitudes between modeled and measured results. In particular, exospheric temperatures determined from Arecibo measurements appear to be suppressed with respect to both middle-latitude temperature determinations and the predictions of MSIS. A tidal analysis of neutral wind determinations from Millstone Hill measurements, however, reveals that middle-latitude meridional mean and diurnal flow was consistent with previous analogous results.

  11. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  13. Parameters of 1-4 mHz (Pc5/Pi3) ULF pulsations during the intervals preceding non-triggered substorms at high geomagnetic latitudes

    NASA Astrophysics Data System (ADS)

    Nosikova, Nataliya; Yagova, Nadezda; Baddeley, Lisa; Kozyreva, Olga; Lorentzen, Dag; Pilipenko, Vyacheslav

    2017-04-01

    One of the important questions for understanding substorm generation is the possible existence of specific pre-substorm variations of plasma, particles and electromagnetic field parameters. In this case analyzing of isolated non-triggered substorms (i.e. substorms that occur under quiet geomagnetic conditions without any visible triggers in IMF or SW) gives benefits for investigation of processes of substorm preparation. It was shown in previous studies that during a few hours preceding a non-triggered isolated substorm, coherent geomagnetic and aurroral luminosity pulsations are observed. Moreover, PSD, amplitudes of geomagnetic fluctuations in Pc5/Pi3 (1-4 mHz) frequency range and some spectral parameters differ from those registered on days without substorms. In present work this sort of pulsations has been studied in details. Features of longitudinal and latitudinal profiles are presented. Possible correlation with ULF disturbances in IMF and SW as well as in the magnetotail/magnetosheath are discussed.

  14. Chinese Mobile Geomagnetic Monitoring Array

    NASA Astrophysics Data System (ADS)

    Chen, Bin; Ni, Zhe; Chen, Shuanggui; Yuan, Jiehao

    2017-04-01

    From 2010, we have set up Chinese Mobile Geomagnetic Monitoring Array (CMGMA) gradually for seismic monitoring and forecasting. Today, the array includes 973 geomagnetic repeat survey stations, the mean intervals between adjacent 2 stations is about 70km in east of China and 150km in west, covers 7'680'000km2 monitoring eara. We measure total intensity (F), declination (D) and indensity (I) on each station one time every year, and then remove dural variation using minutely averages data on the nearest observatory and remove main field using "Chinese Geomagnetic Reference Field (CGRF) -Spherical Cap Harmonic model". After removing secular variation using a natural orthogonal component (NOC) model base hourly averages data from 1995 to now on 31 observatories in China, we calculate the variations of lithosphere magnetic field between each adjacent two years.After analyse the variations of lithoshpere magnetic field before all 25 earthquakes with magnitude bigger than 5 in our monitoring eara, 2 kinds of anomarlies were found during 1-18 months before 20 earthquakes of 25 samples. The first kind was typical called "Quiet Island", and the variant kind called "frozen area" or "quiet byland". The main character of these 2 kind anomalies is the variations of lithosphere magnetic field are smaller near the epicenter than surronding. When we draw the horizontal varistions (ΔBy, ΔBx) as an arrow at level, the variations are identical, scale and direction, in a wide range, as a liquid river flowing from one side to the other.However, the variations near the further epicenter show their difference, with low value and different dirction. Even we have picked these anomlies out before the earthquakes in each July, just soon after our field survey. We are not clear why these nomlies are there, and can not further propose a perfect idea about magnitude and original times.

  15. Pain in the quiet (not red) eye.

    PubMed

    Fiore, David C; Pasternak, Andrew V; Radwan, Rabab M

    2010-07-01

    Although eye pain is often accompanied by redness or injection, pain can also occur with a quiet eye. Pain in a quiet eye can be the first sign of a vision-threatening condition, a more benign ophthalmologic condition, or a nonophthalmologic condition. Acute narrow-angle glaucoma is an emergent vision-threatening condition that requires immediate treatment and referral to an ophthalmologist. Although most nonophthalmologic conditions that cause eye pain do not need immediate treatment, giant cell (temporal) arteritis requires urgent treatment with corticosteroids. Other vascular conditions, such as carotid artery disease, thrombosis of the cavernous sinus, and transient ischemic attack or stroke, rarely cause eye pain but must be considered. Pain may also be referred from the sinuses or from neurologic conditions, such as trigeminal neuralgia, migraine and cluster headaches, and increased intracranial pressure. The differential diagnosis of eye pain in the quiet eye is extensive, necessitating a systematic and thorough approach. (c) 2010 American Academy of Family Physicians.

  16. Composition change and its effect on mass density response during geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Liu, X.; Thayer, J. P.; Wang, W.; Burns, A. G.; Sutton, E.

    2013-12-01

    Accelerometer data from coplanar orbits of CHAMP and GRACE satellites are used to study the complex altitude and latitude variations of the thermosphere mass density response to corotating interaction regions / high speed streams for the period of 01-10 December 2008 near 09 LT. The thermosphere neutral composition response to the energy input and the associated thermal expansion and vertical winds induced by the storm is investigated in this study. Helium number densities near 500 km were extracted from the CHAMP and GRACE measurements and, with three-degree latitude resolution, clearly show the presence of a winter hemisphere helium bulge. Helium estimates in the upper thermosphere during solar minimum have not been observed since the 1976 minimum. This recent extreme solar minimum indicates winter-time helium concentrations exceed NRL-MSISE00 estimates by 30%-70% during quiet geomagnetic activity after adjusting F10.7 input into MSIS. During active geomagnetic conditions, helium concentrations at GRACE altitudes decrease while oxygen concentrations increase. The perturbation in mass density from quiet to active conditions is found to be less enhanced in the winter hemisphere at the higher GRACE altitudes (25%) than at CHAMP altitudes (60%) and is attributed to dynamic behavior in the helium / oxygen transition. An investigation of the altitude structure in thermosphere mass density storm-time perturbations revealed the important effects of composition change with maximum perturbation occurring near the He/O transition region and a much weaker maximum occurring near the O/N2 transition region. A helium module has been implemented in the NCAR-TIEGCM model and simulations of mass density response to a geomagnetic storm for thermosphere conditions with and without helium will be presented.

  17. 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.

  18. Effects of geomagnetic activity and atmospheric power variations on quantitative measures of brain activity: Replication of the Azerbaijani studies

    NASA Astrophysics Data System (ADS)

    Mulligan, Bryce P.; Hunter, Mathew D.; Persinger, Michael A.

    2010-04-01

    This study replicates and extends the observations by Babayev and Allahveriyeva that changes in right hemispheric electroencephalographic activity are correlated with increases in geomagnetic activity. During the geomagnetically quiet interface between solar cycle 23 and 24 quantitative electroencephalographic (QEEG) measurements were completed for normal young adults in three separate experiments involving about 120 samples over 1.5 years. The most consistent, moderate strength correlations occurred for the changes in power within the gamma and theta ranges over the right frontal lobe. Real-time measures of atmospheric power obtained from polar orbiting satellites showed similar effects. The preferential involvement of the right frontal lobe and the regions subject to its inhibition with environmental energetic changes are consistent with the behavioural correlations historically associated with these conditions. They include increased incidence of emotional lability, erroneous reconstruction of experiences, social confrontations, and unusual perceptions.

  19. Geomagnetic Storm Impact On GPS Code Positioning

    NASA Astrophysics Data System (ADS)

    Uray, Fırat; Varlık, Abdullah; Kalaycı, İbrahim; Öǧütcü, Sermet

    2017-04-01

    This paper deals with the geomagnetic storm impact on GPS code processing with using GIPSY/OASIS research software. 12 IGS stations in mid-latitude were chosen to conduct the experiment. These IGS stations were classified as non-cross correlation receiver reporting P1 and P2 (NONCC-P1P2), non-cross correlation receiver reporting C1 and P2 (NONCC-C1P2) and cross-correlation (CC-C1P2) receiver. In order to keep the code processing consistency between the classified receivers, only P2 code observations from the GPS satellites were processed. Four extreme geomagnetic storms October 2003, day of the year (DOY), 29, 30 Halloween Storm, November 2003, DOY 20, November 2004, DOY 08 and four geomagnetic quiet days in 2005 (DOY 92, 98, 99, 100) were chosen for this study. 24-hour rinex data of the IGS stations were processed epoch-by-epoch basis. In this way, receiver clock and Earth Centered Earth Fixed (ECEF) Cartesian Coordinates were solved for a per-epoch basis for each day. IGS combined broadcast ephemeris file (brdc) were used to partly compensate the ionospheric effect on the P2 code observations. There is no tropospheric model was used for the processing. Jet Propulsion Laboratory Application Technology Satellites (JPL ATS) computed coordinates of the stations were taken as true coordinates. The differences of the computed ECEF coordinates and assumed true coordinates were resolved to topocentric coordinates (north, east, up). Root mean square (RMS) errors for each component were calculated for each day. The results show that two-dimensional and vertical accuracy decreases significantly during the geomagnetic storm days comparing with the geomagnetic quiet days. It is observed that vertical accuracy is much more affected than the horizontal accuracy by geomagnetic storm. Up to 50 meters error in vertical component has been observed in geomagnetic storm day. It is also observed that performance of Klobuchar ionospheric correction parameters during geomagnetic storm

  20. The NASA quiet engines

    NASA Technical Reports Server (NTRS)

    Ciepluch, C. C.

    1972-01-01

    Efforts to develop an engine noise reduction technology suitable for use on subsonic and conventional takeoff and landing type aircraft are reported. Two baseline quiet engines were developed and tested. The engines were designed with the following quiet features: (1) high bypass ratio engine, (2) large rotor-stator spacing of rotor chords, (3) reduced rotor tip speeds, (4) sound absorbing liners in inlet-outlet ducts, and (5) an optimum ratio from stator to rotor blades. Test results show that if these features are applied to future aircraft, substantial reduction in aircraft noise levels will be obtained.

  1. Rapid and Quiet Drill

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph; Chang, Zensheu; Bao, Xiaoqi

    2007-01-01

    This describes aspects of the rapid and quiet drill (RAQD), which is a prototype apparatus for drilling concrete or bricks. The design and basic principle of operation of the RAQD overlap, in several respects, with those of ultrasonic/ sonic drilling and coring apparatuses described in a number of previous NASA Tech Briefs articles. The main difference is that whereas the actuation scheme of the prior apparatuses is partly ultrasonic and partly sonic, the actuation scheme of the RAQD is purely ultrasonic. Hence, even though the RAQD generates considerable sound, it is characterized as quiet because most or all of the sound is above the frequency range of human hearing.

  2. 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.

  3. A Mostly Quiet Pacific

    NASA Image and Video Library

    2003-11-18

    Some climate forecast models indicate there is an above average chance that there could be a weak to borderline El Niño by the end of November 2003. However, the trade winds, blowing from east to west across the equatorial Pacific Ocean, remain strong. Thus, there remains some uncertainty among climate scientists as to whether the warm temperature anomaly will form again this year. The latest remote sensing data from NASA's Jason satellite show near normal conditions across the equatorial Pacific. There are currently no visible signs in sea surface height of an impending El Niño. This equatorial quiet contrasts with the Bering Sea, Gulf of Alaska and U.S. West Coast where lower-than-normal sea surface levels and cool ocean temperatures continue (indicated by blue and purple areas). The image above is a global map of sea surface height, accurate to within 30 millimeters. The image represents data collected and composited over a 10-day period, ending on Nov. 3, 2003. The height of the water relates to the temperature of the water. As the ocean warms, its level rises; and as it cools, its level falls. Yellow and red areas indicate where the waters are relatively warmer and have expanded above sea level, green indicates near normal sea level, and blue and purple areas show where the waters are relatively colder and the surface is lower than sea level. The blue areas are between 5 and 13 centimeters (2 and 5 inches) below normal, whereas the purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. http://photojournal.jpl.nasa.gov/catalog/PIA04878

  4. 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.

  5. Microbial proteomics: the quiet revolution

    SciTech Connect

    Seraphin, Bertrand; Hettich, Robert {Bob} L

    2012-01-01

    Technological developments in DNA sequencing and their application to study thousands of microbial genomes or even microbial ecosystems still today often make the headlines of general newspapers and scientific journals. These revolutionary changes are hiding another revolution that is unfolding more quietly in the background: the development of microbial proteomics to study genome expression products. It is important to recognize that while DNA sequencing reveals extensive details about the genomic potential of an organism or community, proteomic measurements reveal the functional gene products that are present and operational under specific environmental conditions, and thus perhaps better characterize the critical biomolecules that execute the life processes (enzymes, signaling, structural factors, etc.).

  6. The Quiet Skies Project

    ERIC Educational Resources Information Center

    Rapp, Steve

    2008-01-01

    To help promote student awareness of the connection between radio astronomy and radio frequency interference (RFI), an inquiry-based science curriculum was developed to allow high school students to determine RFI levels in their communities. The Quiet Skies Project--the result of a collaboration between the National Aeronautics and Space…

  7. The Quiet Skies Project

    ERIC Educational Resources Information Center

    Rapp, Steve

    2008-01-01

    To help promote student awareness of the connection between radio astronomy and radio frequency interference (RFI), an inquiry-based science curriculum was developed to allow high school students to determine RFI levels in their communities. The Quiet Skies Project--the result of a collaboration between the National Aeronautics and Space…

  8. Correcting solar quiet variations for tidal signals

    NASA Astrophysics Data System (ADS)

    Guzavina, Martina; Grayver, Alexander; Kuvshinov, Alexey

    2017-04-01

    Solar quiet (Sq) variations of geomagnetic field are originated from electric current system which is flowing at 110 km altitude in a thin ionospheric E-layer. This current system is driven by atmospheric tides in the ambient magnetic field of the Earth. These tides are generated from solar heating of the atmosphere on the sunlit side of Earth. Sq variations are periodic phenomenon and thus can be represented as a superposition of time harmonics with periods of 24, 12, 8, 6, 4.8 and 4 hours. These variations can be used for electromagnetic induction sounding to study electrical conductivity of the Earth's upper mantle down to approximately 600 km. However, Sq variations are potentially distorted by several factors. Among them are motionally-induced (tidal) magnetic signals which have periods close to 12 and 24 hours. This study is aimed at evaluating and correcting for the effect of tidal magnetic signals in observed Sq variations.

  9. 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.

  10. Solar activity dependence of nightside aurora in winter conditions

    NASA Astrophysics Data System (ADS)

    Zhou, Su; Luan, Xiaoli; Dou, Xiankang

    2016-02-01

    The dependence of the nightside (21:00-03:00 MLT; magnetic local time) auroral energy flux on solar activity was quantitatively studied for winter/dark and geomagnetically quiet conditions. Using data combined from Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager and Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager observations, we separated the effects of geomagnetic activity from those of solar flux on the nightside auroral precipitation. The results showed that the nightside auroral power was reduced by ~42% in solar maximum (F10.7 = 200 sfu; solar flux unit 1 sfu = 10-22 W m-2 Hz-1) with respect to that under solar minimum (F10.7 = 70 sfu) for the Kp = 1 condition, and this change rate became less (~21%) for the Kp = 3 condition. In addition, the solar cycle dependence of nightside auroral power was similar with that from both the premidnight (21:00-23:00 MLT) and postmidnight (01:00-03:00 MLT) sectors. These results indicated that as the ionospheric ionization increases with the enhanced auroral and geomagnetic activities, the solar activity dependences of nightside auroral power become weaker, at least under geomagnetically quiet conditions.

  11. What is magnetically quiet time?

    NASA Astrophysics Data System (ADS)

    Friel, M. M.; Gjerloev, J. W.; Ohtani, S.; Martin, P.; Muhleisen, M.; Olsen, N.; Korth, H.; Foerland, B.

    2015-12-01

    We present the new SuperMAG Disturbance Level indices SMDL_hi (> 55 deg MLat) and SMDL_lo (<55 deg MLat). These indices objectively quantify the external magnetic field perturbations with a 1 min temporal resolution appropriate for the magnetosphere-ionosphere (M-I) system (reconfiguration time ~10 min). The indices are derived from all the ground based magnetometer stations that are part of the SuperMAG collaboration and thus they have the sufficient spatial coverage. Historically the selection of the quietest days (Q-days) and most disturbed days (D-days) of each month is deduced from the Kp indices. Other techniques include the use of magnetic indices and solar wind conditions. Common for these techniques is the long list of assumptions on which they are based. For example: duration of quiet period (e.g. 1 hour or 24 hours), start of quiet periods (e.g. 0 UT), inferred response of the magnetosphere-ionosphere system to solar wind conditions, and the ability of the magnetic indices to quantify the external field contributions (e.g. using only north-south component). We show that previous published techniques include periods of intense substorms and magnetic storms while SMDL effectively excludes these disturbances. The SMDL indices provides more temporal coverage through better quantification of the external field component. We show events, statistics, and we show that the SMDL index provides a powerful tool to quantify the external field contribution.

  12. 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.

  13. Refining the Jurassic Magnetic Quiet Zone

    NASA Astrophysics Data System (ADS)

    Tominaga, M.; Tivery, M.; Sager, W. W.

    2016-12-01

    We present a coherent marine magnetic reversal record from the Pacific to refine the Jurassic Quiet Zone (JQZ). Our definitive magnetic anomaly record consists of high-resolution sea surface, mid-water (3-km level deep-towed), and near-bottom profiles (0.1-km to the seafloor) with the magnetic source layer constrained by gravity anomaly data and reflection and refraction seismics, all of which are newly collected during TN272 and SKQ2014S2 cruises. All magnetic anomaly data were corrected diurnal variations and the present-day ambient geomagnetic field. In comparing our three-level JQZ magnetic anomaly profiles with previous work in the Japanese lineations, we confirm a globally coherent anomaly sequence in the JQZ from M29 to M42, including the distinctive amplitude envelope decreasing back in time from M19 to M38, with a minimum at M41, and then increasing back in time. A strong similarity in the M37/M38 polarity attributes found both in magnetostratigraphic and marine magnetic records suggest that rapid magnetic reversals were occurring during the M38 time in the JQZ. Seismic and gravity profiles from the Hawaiian JQZ seafloor show late-stage Cretaceous volcanism thickening crust by up to 150% with extra melt emplaced at the Moho, and numerous sills and volcanic cones in the sediment and on the seafloor. The region of thickest crust in the Hawaiian lineation corridor coincides with the region of the lowest JQZ anomaly amplitudes, very similar to the Low Amplitude Zone of Japanese lineation sequence, suggesting that the JQZ anomaly character can represent changes in geomagnetic field intensity over time but is free of the effects of Cretaceous volcanic overprint. We conducted inversion modeling to establish polarity block models and to estimate reversal rates. Reversal rates are the highest during periods with the lowest anomaly amplitudes, indicating a unique period of geomagnetic field behavior in the Earth's history.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  15. Quiet engine program flight engine design study

    NASA Technical Reports Server (NTRS)

    Klapproth, J. F.; Neitzel, R. E.; Seeley, C. T.

    1974-01-01

    The results are presented of a preliminary flight engine design study based on the Quiet Engine Program high-bypass, low-noise turbofan engines. Engine configurations, weight, noise characteristics, and performance over a range of flight conditions typical of a subsonic transport aircraft were considered. High and low tip speed engines in various acoustically treated nacelle configurations were included.

  16. 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.

  17. Search for seasonal rhythmicity of pineal melatonin production in rats under constant laboratory conditions: spectral chronobiological analysis, and relation to solar and geomagnetic variables.

    PubMed

    Bartsch, Hella; Mecke, Dieter; Probst, Hansgeorg; Küpper, Heinz; Seebald, Eckard; Salewski, Lothar; Stehle, Thilo; Bartsch, Christian

    2012-10-01

    Earlier we reported that in a number of experiments pineal melatonin production in rats under constant laboratory conditions displayed seasonal rhythms but subsequently were not always able to confirm this. Since there was no indication under which conditions such rhythms may be present, we performed four consecutive identical experiments with untreated female Sprague-Dawley rats within the same animal room during 1997-2006. Nocturnal urine samples (19-23, 23-3, 3-7 h) were collected at monthly intervals over 494-658 d with 12 animals each in experiments I and II (1997-1999, 1999-2000), 30 animals in experiment III (2002-2004), and 15 in experiment IV (2005-2006). 6-Sulfatoxymelatonin (aMT6s) was measured by ELISA. The excreted aMT6s at each time interval as well as total nocturnal aMT6s-excretion (19-7 h) was submitted to standard statistical analyses as well as to a spectral chronobiological analysis to determine the period lengths of the components involved which was followed by processing with the single cosinor method. Seasonal rhythm components (circannual period length: 360 ± 60 d) were detected in experiment III (2002-2004) for the overall nocturnal excretion as well as for two sub-intervals (23-3 and 3-7 h) and in one night interval of experiment II (23-3 h). Multiple components with mostly short period lengths of around 100 d and some long ones of 500-650 d were found in the other experiments. Systematic MESOR and amplitude variations were observed during the experiments, being highest in experiment II (19-7 h, also 23-3 h and 3-7 h) and lowest in experiments I and IV. These results illustrate that seasonal melatonin rhythms are not a general phenomenon in female laboratory rats indicating an involvement of unknown environmental cues. As an extension of our earlier hypothesis regarding a seasonal Zeitgeber function of the horizontal intensity H of the geomagnetic field showing circannual variations, we assume further modulation by the 11-yrs' sunspot

  18. 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.

  19. Morphological changes in the retina in Pacific ocean salmon Oncorhynchus masou fry in response to neutralization of the geomagnetic field in conditions of normal illumination.

    PubMed

    Maksimovich, A A; Kondrashev, S L; Gnyubkina, V P

    2008-10-01

    The studies reported here provide the first demonstration that retinal responses in both the fry of the migratory salmon trout Oncorhynchus masou and the dwarf form of this species changed in conditions of experimental neutralization of the geomagnetic field (GMF); migratory salmon trout fry and dwarves showed different changes. The responses of different types of retinal photoreceptor in migratory salmon trout fry to neutralization of the GMF differed: while rods and double cones perceived neutralization of the GMF as the onset of darkness (the scotopic reaction), single (generally blue-sensitive) cones responded to neutralization of the GMF both as presentation of blue light or (very rarely) ultraviolet irradiation. The retina of dwarf male salmon trout responded to neutralization of the GMF with a double response: rods showed a light (photopic) response, while double (red/green-sensitive) cones produced dark (scotopic) responses. Single (blue-sensitive) cones responded to neutralization of the GMF as bright blue light. Thus, the morphological picture of the retina in dwarf male salmon trout in these experimental conditions corresponds to the perception of blue light. The initial conditions were different--normal diffuse daylight with a brightness of about 7.5 Lx. It is likely that neutralization of the magnetic field had no effect on rods, while double, red-green, cones responded as to darkness, i.e., the fish did not perceive red or green light in the visible spectrum, but perceived only blue and, possibly, ultraviolet light by means of central blue-sensitive and accessory cones. Thus, these experiments demonstrated that in conditions of normal daylight illumination, retinal photoreceptors in salmon fry respond to changes in the earth's magnetic field, i.e., objectively function as magnetoreceptors.

  20. Simulation of Theoretical Most-Extreme Geomagnetic Sudden Commencements

    NASA Astrophysics Data System (ADS)

    Welling, D. T.; Love, J. J.; Wiltberger, M. J.; Rigler, E. J.

    2016-12-01

    We report results from a numerical simulation of geomagnetic sudden commencements driven by solar wind conditions given by theoretical-limit extreme coronal-mass ejections (CMEs) estimated by Tsurutani and Lakhina [2014]. The CME characteristics at Earth are a step function that jumps from typical quiet values to 2700 km/s flow speed and a magnetic field magnitude of 127 nT. These values are used to drive three coupled models: a global magnetohydrodynamic (MHD) magnetospheric model (BATS-R-US), a ring current model (the Rice Convection Model, RCM), and a height-integrated ionospheric electrodynamics model (the Ridley Ionosphere Model, RIM), all coupled together using the Space Weather Modeling Framework (SWMF). Additionally, simulations from the Lyon-Fedder-Mobarry MHD model are performed for comparison. The commencement is simulated with both purely northward and southward IMF orientations. Low-latitude ground-level geomagnetic variations, both B and dB/dt, are estimated in response to the storm sudden commencement. For a northward interplanetary magnetic field (IMF) storm, the combined models predict a maximum sudden commencement response, Dst-equivalent of +200 nT and a maximum local dB/dt of 200nT/s. While this positive Dst response is driven mainly by magnetopause currents, complicated and dynamic Birkeland current patterns also develop, which drive the strong dB/dt responses at high latitude. For southward IMF conditions, erosion of dayside magnetic flux allows magnetopause currents to approach much closer to the Earth, leading to a stronger terrestrial response (Dst-equivalent of +250 nT). Further, high latitude signals from Region 1 Birkeland currents move to lower latitudes during the southward IMF case, increasing the risk to populated areas around the globe. Results inform fundamental understanding of solar-terrestrial interaction and benchmark estimates for induction hazards of interest to the electric-power grid industry.

  1. Simulation of Theoretical Most-Extreme Geomagnetic Sudden Commencements

    NASA Astrophysics Data System (ADS)

    Welling, Daniel; Love, Jeffrey; Wiltberger, Michael; Rigler, Erin; Gombosi, Tamas

    2016-04-01

    We report results from a numerical simulation of geomagnetic sudden commencements driven by solar wind conditions given by theoretical-limit extreme coronal-mass ejections (CMEs) estimated by Tsurutani and Lakhina [2014]. The CME characteristics at Earth are a step function that jumps from typical quiet values to 2700 km/s flow speed and a magnetic field magnitude of 127 nT. These values are used to drive three coupled models: a global magnetohydrodynamic (MHD) magnetospheric model (BATS-R-US), a ring current model (the Rice Convection Model, RCM), and a height-integrated ionospheric electrodynamics model (the Ridley Ionosphere Model, RIM), all coupled together using the Space Weather Modeling Framework (SWMF). Additionally, simulations from the Lyon-Fedder-Mobarry MHD model are performed for comparison. The commencement is simulated with both purely northward and southward IMF orientations. Low-latitude ground-level geomagnetic variations, both B and dB/dt, are estimated in response to the storm sudden commencement. For a northward interplanetary magnetic field (IMF) storm, the combined models predict a maximum sudden commencement response, Dst-equivalent of +200 nT and a maximum local dB/dt of ~200nT/s. While this positive Dst response is driven mainly by magnetopause currents, complicated and dynamic Birkeland current patterns also develop, which drive the strong dB/dt responses at high latitude. For southward IMF conditions, erosion of dayside magnetic flux allows magnetopause currents to approach much closer to the Earth, leading to a stronger terrestrial response (Dst-equivalent of +250 nT). Further, high latitude signals from Region 1 Birkeland currents move to lower latitudes during the southward IMF case, increasing the risk to populated areas around the globe. Results inform fundamental understanding of solar-terrestrial interaction and benchmark estimates for induction hazards of interest to the electric-power grid industry.

  2. A note on current sheet stress balance in the geomagnetic tail for asymmetrical tail lobe plasma conditions

    NASA Astrophysics Data System (ADS)

    Owen, C. J.; Cowley, S. W. H.

    1987-04-01

    It is shown that the current sheet equilibrium condition can be readily generalized to include lobe plasma asymmetry under the simplifying assumption that all particles incident on the current sheet are transmitted through it. The result is expressed in a form which emphasizes the physical equivalence of stress balance by anisotropic plasma pressure and by net flow through the current sheet. The former case occurs for symmetrical lobe conditions, and balance is expressed in terms of the marginal firehose stability condition. The latter case occurs if one lobe dominates, when the field-aligned plasma flow speed in the field line rest frame must equal the tail lobe Alfven speed. Results are illustrated by a simple example in which the inflow plasmas are approximated as cold ion beams of unequal density and speed. It is shown that equilibrium solutions cease to exist for sufficiently large inflow velocity shears, but that in practice this condition is most unlikely to be encountered in the tail.

  3. The QUIET Instrument

    NASA Technical Reports Server (NTRS)

    Gaier, T.; Kangaslahti, P.; Lawrence, C. R.; Leitch, E. M.; Wollack, E. J.

    2012-01-01

    The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the Cosmic Microwave Background, targeting the imprint of inflationary gravitational waves at large angular scales ( approx 1 deg.) . Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4 m side-fed Dragonian telescope. The polarimeters which form the focal planes use a highly compact design based on High Electron Mobility Transistors (HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U, and I in a single module. The 17-element Q-band polarimeter array, with a central frequency of 43.1 GHz, has the best sensitivity (69 micro Ks(exp 1/2)) and the lowest instrumental systematic errors ever achieved in this band, contributing to the tensor-to-scalar ratio at r < 0.1. The 84-element W-band polarimeter array has a sensitivity of 87 micro Ks(exp 1/2) at a central frequency of 94.5 GHz. It has the lowest systematic errors to date, contributing at r < 0.01 (QUIET Collaboration 2012) The two arrays together cover multipoles in the range l approximately equals 25-975 . These are the largest HEMT-ba.sed arrays deployed to date. This article describes the design, calibration, performance of, and sources of systematic error for the instrument,

  4. 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).

  5. Diurnal variation of galactic cosmic ray intensity on quiet days

    NASA Technical Reports Server (NTRS)

    Kumar, S.; Datt, S. C.

    1985-01-01

    A detailed study of the diurnal variation on long term basis was performed on geomagnetically quiet days using the experimental data of the cosmic ray intensity from the worldwide neutron monitoring stations. During the period when the polarity of the solar magnetic field in the Northern Hemisphere of the sun is negative the phase and amplitude of the diurnal anisotropy on quiet days was observed to remain almost constant. When the polarity of solar magnetic field in the Northern Hemisphere changes from negative to positive, a shift in the phase of the diurnal anisotropy on quiet days towards earlier hours is observed and the shift is found to be maximum during minimum solar activity periods 1953-54 and 1975-76. When the polarity of solar magnetic field changes from positive to negative in the Northern Hemisphere of the Sun the phase of the diurnal anisotropy on quiet days recovers to its usual direction of corotational anisotropy and is observed to remain almost constant till the polarity of the solar magnetic field does not change.

  6. Influence of geomagnetic storms of September 26-30, 2011, on the ionosphere and HF radiowave propagation. II. radiowave propagation

    NASA Astrophysics Data System (ADS)

    Kotova, D. S.; Klimenko, M. V.; Klimenko, V. V.; Zakharov, V. E.

    2017-05-01

    A study of HF wave propagation in the three-dimensional inhomogeneous ionosphere has been carried out in an approximation of geometrical optics. The three-dimensional medium of radio wave propagation is considered to be inhomogeneous, absorbing, and anisotropic due to the influence of the geomagnetic field. The parameters of the medium are described by the results of calculations on the basis of the Global Self-Consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP). The propagation of radio waves in the equatorial, middle-, and high-latitude ionosphere was studied. Comparisons of the ray trajectories, integral attenuation, deviations of the projection of radio wave trajectories onto the Earth's surface from the great-circle arc, and the behavior of the angle between the wave phase and wave energy directions, as well as the angle between the direction of propagation and the external magnetic field obtained for quiet and disturbed conditions, have been performed. We consider a geomagnetic storm that occurred in 2011, with the main storm phase occurring on September 26, and the day after geomagnetic disturbances, September 29, as disturbed conditions in the ionosphere.

  7. Solar-geomagnetic activity and Aa indices toward a standard classification

    NASA Astrophysics Data System (ADS)

    Ouattara, Frédéric; Amory-Mazaudier, Christine

    2009-12-01

    Legrand and Simon [1989. Solar cycle and geomagnetic activity: a review for geophysicists. Part I. The contributions to geomagnetic activity of shock waves and of the solar wind. Annales Geophysicae 7(6), 565-578] classified one century (1868-1978) of geomagnetic activity, using the Mayaud's Aa index, in four classes related to solar activity: (1) the magnetic quiet activity due to slow solar wind flowing around the magnetosphere, (2) the recurrent activity related to high wind speed solar wind, (3) the fluctuating activity related to fluctuating solar wind and (4) the shock activity due to shock events (CME). In this paper, we use this classification to analyse the solar-geomagnetic activity from 1978 to 2005. We found that during the last three decades the level of geomagnetic quiet activity estimated by Aa indices is decreasing: 2003 is the year of the smallest level of quiet geomagnetic activity since 1868. We compare Legrand and Simon's classification with new in situ solar wind data [Richardson, I.G., Cliver, E.W., Cane, H.V., 2000. Sources of geomagnetic activity over the solar cycle: relative importance of coronal mass ejections, high-speed streams, and slow solar wind. Journal of Geophysical research 105(A8), 18,200-18,213; Richardson, I.G., Cane, H.V., 2002. Sources of geomagnetic activity during nearly three solar cycles (1972-2000). Journal of Geophysical Research 107(A8), 1187] and find a rather good agreement. The differences are only due to minor definitions of the extent of the classes. An attempt is made at defining a more precise standard classification of solar phenomena and at defining time scales of these to understand more precisely the geomagnetic signatures of solar activity.

  8. 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.

  9. 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.

  10. A description of the external and internal quiet daily variation currents at North American locations for a quiet-Sun year.

    USGS Publications Warehouse

    Campbell, W.H.

    1983-01-01

    An order 4, degree 12 spherical harmonic analysis of the smoothed quiet geomagnetic daily variations was used to separate the external and internal geomagnetic Sq field at North American locations for the quiet-Sun year, 1965. These fields were represented by a month-by-month display of equivalent current vortex systems with dominant, pre-noon foci. The focus reached 40o latitude near the June solstice and about 30o latitude near the December solstice. The daily range of Sq current amplitudes was largest in late July to early August and smallest in mid-December. Semi-annual variations of Sq currents dominated only the equatorial region. Daily maxima in mid-latitudes, occurred mostly near local noon in December to February and about 1 hr before noon in June to mid-October. -Author

  11. On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

    NASA Astrophysics Data System (ADS)

    Kauristie, K.; Morschhauser, A.; Olsen, N.; Finlay, C. C.; McPherron, R. L.; Gjerloev, J. W.; Opgenoorth, H. J.

    2016-12-01

    We present a review on geomagnetic indices describing global geomagnetic storm activity (Kp, am, Dst and dDst/dt) and on indices designed to characterize high latitude currents and substorms (PC and AE-indices and their variants). The focus in our discussion is in main field modelling, where indices are primarily used in data selection criteria for weak magnetic activity. The publicly available extensive data bases of index values are used to derive joint conditional Probability Distribution Functions (PDFs) for different pairs of indices in order to investigate their mutual consistency in describing quiet conditions. This exercise reveals that Dst and its time derivative yield a similar picture as Kp on quiet conditions as determined with the conditions typically used in internal field modelling. Magnetic quiescence at high latitudes is typically searched with the help of Merging Electric Field (MEF) as derived from solar wind observations. We use in our PDF analysis the PC-index as a proxy for MEF and estimate the magnetic activity level at auroral latitudes with the AL-index. With these boundary conditions we conclude that the quiet time conditions that are typically used in main field modelling ( PC<0.8, Kp<2 and |Dst|<30 nT) correspond to weak auroral electrojet activity quite well: Standard size substorms are unlikely to happen, but other types of activations (e.g. pseudo breakups AL>-300 nT) can take place, when these criteria prevail. Although AE-indices have been designed to probe electrojet activity only in average conditions and thus their performance is not optimal during weak activity, we note that careful data selection with advanced AE-variants may appear to be the most practical way to lower the elevated RMS-values which still exist in the residuals between modeled and observed values at high latitudes. Recent initiatives to upgrade the AE-indices, either with a better coverage of observing stations and improved baseline corrections (the Super

  12. On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

    NASA Astrophysics Data System (ADS)

    Kauristie, K.; Morschhauser, A.; Olsen, N.; Finlay, C. C.; McPherron, R. L.; Gjerloev, J. W.; Opgenoorth, H. J.

    2017-03-01

    We present a review on geomagnetic indices describing global geomagnetic storm activity ( Kp, am, Dst and dDst/dt) and on indices designed to characterize high latitude currents and substorms ( PC and AE-indices and their variants). The focus in our discussion is in main field modelling, where indices are primarily used in data selection criteria for weak magnetic activity. The publicly available extensive data bases of index values are used to derive joint conditional Probability Distribution Functions (PDFs) for different pairs of indices in order to investigate their mutual consistency in describing quiet conditions. This exercise reveals that Dst and its time derivative yield a similar picture as Kp on quiet conditions as determined with the conditions typically used in internal field modelling. Magnetic quiescence at high latitudes is typically searched with the help of Merging Electric Field ( MEF) as derived from solar wind observations. We use in our PDF analysis the PC-index as a proxy for MEF and estimate the magnetic activity level at auroral latitudes with the AL-index. With these boundary conditions we conclude that the quiet time conditions that are typically used in main field modelling (PC<0.8, Kp<2 and |Dst|<30 nT) correspond to weak auroral electrojet activity quite well: Standard size substorms are unlikely to happen, but other types of activations (e.g. pseudo breakups AL>-300 nT) can take place, when these criteria prevail. Although AE-indices have been designed to probe electrojet activity only in average conditions and thus their performance is not optimal during weak activity, we note that careful data selection with advanced AE-variants may appear to be the most practical way to lower the elevated RMS-values which still exist in the residuals between modeled and observed values at high latitudes. Recent initiatives to upgrade the AE-indices, either with a better coverage of observing stations and improved baseline corrections (the Super

  13. Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: the importance of nitric oxide

    NASA Astrophysics Data System (ADS)

    Kirkwood, S.; Belova, E.; Dalin, P.; Mihalikova, M.; Mikhaylova, D.; Murtagh, D.; Nilsson, H.; Satheesan, K.; Urban, J.; Wolf, I.

    2013-02-01

    The relationship between polar mesosphere summer echoes (PMSE) and geomagnetic disturbances (represented by magnetic K indices) is examined. Calibrated PMSE reflectivities for the period May 2006-February 2012 are used from two 52.0/54.5 MHz radars located in Arctic Sweden (68° N, geomagnetic latitude 65°) and at two different sites in Queen Maud Land, Antarctica (73°/72° S, geomagnetic latitudes 62°/63°). In both the Northern Hemisphere (NH) and the Southern Hemisphere (SH) there is a strong increase in mean PMSE reflectivity between quiet and disturbed geomagnetic conditions. Mean volume reflectivities are slightly lower at the SH locations compared to the NH, but the position of the peak in the lognormal distribution of PMSE reflectivities is close to the same at both NH and SH locations, and varies only slightly with magnetic disturbance level. Differences between the sites, and between geomagnetic disturbance levels, are primarily due to differences in the high-reflectivity tail of the distribution. PMSE occurrence rates are essentially the same at both NH and SH locations during most of the PMSE season when a sufficiently low detection threshold is used so that the peak in the lognormal distribution is included. When the local-time dependence of the PMSE response to geomagnetic disturbance level is considered, the response in the NH is found to be immediate at most local times, but delayed by several hours in the afternoon sector and absent in the early evening. At the SH sites, at lower magnetic latitude, there is a delayed response (by several hours) at almost all local times. At the NH (auroral zone) site, the dependence on magnetic disturbance is highest during evening-to-morning hours. At the SH (sub-auroral) sites the response to magnetic disturbance is weaker but persists throughout the day. While the immediate response to magnetic activity can be qualitatively explained by changes in electron density resulting from energetic particle

  14. On the definition of geomagnetic activity: Case study at the auroral Sodankylä station

    NASA Astrophysics Data System (ADS)

    Martini, D.; Mursula, K.; Ulich, T.; Kultima, J.

    2009-12-01

    Here we demonstrate that the traditional separation of regular (Sq) and irregular geomagnetic variations is not a straightforward process at high latitudes. We use various methods in estimating the local geomagnetic activity at the auroral Sodankylä station, and compare their long-term properties. We show that at high-latitude the magnetic quiet daily curve cannot be classified purely as regular variation but, rather, an imprint of such current systems in the ionosphere and magnetosphere that are the actual causes of the irregular variations. That is, in this region the Sq variation is an organic part of geomagnetic activity itself. We also show that excluding certain part of the daily activity when defining a geomagnetic index, as in case of the IHV (Inter-Hourly Variability) index, leads to an estimate that inherently differs in its response to solar wind drivers from the other three hourly K-based measures of geomagnetic activity with full day coverage.

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

    PubMed

    Conesa, J

    1995-06-01

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

  16. [A method for studying the effect of the geomagnetic field on the vital activities of microorganisms in the enteric family].

    PubMed

    Chernoshchekov, K A

    1989-09-01

    The proposed method makes it possible to find out the direct influence of the geomagnetic field (GMF) on microorganisms of the family Enterobacteriaceae (the genera Escherichia, Shigella, Salmonella). Different disturbances in the state of GMF, both in amplitude and frequency range, were modeled under laboratory conditions. Microbial cells were cultivated in sterile artesian-well water or physiological saline with no organic substrate added. Experiments were performed at room temperature for 5 and more days. In these experiments the standard dose of microbial suspension was inoculated daily into Endo medium. The differences in the reproductive capacity and survival time of microorganisms in the test and control vials were compared with the indices of geomagnetic disturbances. If the experiments were started 2-4 days before the appearance of geomagnetic disturbances, the suppression of the reproductive capacity of microorganisms occurred, then followed its stimulation; this phenomenon particularly affected Escherichia coli and Shigella sonnei. In case of the quiet state of GMF the suppression of reproductive capacity is commonly observed. If the beginning of the experiment coincides with the appearance of a magnetic storm, a sharp decrease in the reproductive capacity of microorganisms and the death of the population within 1-5 days usually occurred. The survival rate of microorganisms depended on the state of GMF disturbances. The survival time of cell generations during disturbances of GMF was considerably longer. Under the conditions of a superimposed magnetic field the reproductive capacity of microorganisms outstrips, as a rule, that developing under the conditions of the compensation of the field. Studies on the biological activity of infralow frequency showed that the multidirectional reproductivity effect was observed due to constant changes in the geomagnetic background.

  17. Investigation of the temperature gradient instability as the source of midlatitude quiet time decameter-scale ionospheric irregularities: 1. Observations

    NASA Astrophysics Data System (ADS)

    Larquier, S.; Eltrass, A.; Mahmoudian, A.; Ruohoniemi, J. M.; Baker, J. B. H.; Scales, W. A.; Erickson, P. J.; Greenwald, R. A.

    2014-06-01

    Super Dual Auroral Radar Network (SuperDARN) radars regularly observe decameter-scale ionospheric irregularities at midlatitudes during quiet geomagnetic conditions. The mechanism responsible for the growth of such irregularities is still unknown. Previous results based on data from the Wallops SuperDARN HF radar and Incoherent Scatter Radar have suggested that the Temperature Gradient Instability (TGI) could be responsible for only part of the observed irregularities. This conclusion was reached based on the relative orientation of horizontal electron temperature and density gradients. However, the TGI theory requires driving gradients to be perpendicular to perpendicular to the geomagnetic field B. Since midlatitude field lines are approximately 20° off vertical, we have reexamined the original data and computed gradients along the meridional direction perpendicular to B. Distinctions have to be made between the topside and bottomside F region due to the strong influence of vertical gradients. We find that the TGI growth is possible in the topside F region for the duration of the experiment, even before irregularities were observed. We show that the absence of observed irregularities during favorable TGI growth conditions is not a consequence of HF propagation but of higher E region electron irregularity growth. We conclude that the TGI is a valid mechanism to explain the generation of all irregularities observed during the experiment.

  18. 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.

  19. Geomagnetically Induced Currents: Principles

    NASA Astrophysics Data System (ADS)

    Oliveira, Denny M.; Ngwira, Chigomezyo M.

    2017-10-01

    The geospace, or the space environment near Earth, is constantly subjected to changes in the solar wind flow generated at the Sun. The study of this environment variability is called Space Weather. Examples of effects resulting from this variability are the occurrence of powerful solar disturbances, such as coronal mass ejections (CMEs). The impact of CMEs on the Earth's magnetosphere very often greatly perturbs the geomagnetic field causing the occurrence of geomagnetic storms. Such extremely variable geomagnetic fields trigger geomagnetic effects measurable not only in the geospace but also in the ionosphere, upper atmosphere, and on and in the ground. For example, during extreme cases, rapidly changing geomagnetic fields generate intense geomagnetically induced currents (GICs). Intense GICs can cause dramatic effects on man-made technological systems, such as damage to high-voltage power transmission transformers leading to interruption of power supply, and/or corrosion of oil and gas pipelines. These space weather effects can in turn lead to severe economic losses. In this paper, we supply the reader with theoretical concepts related to GICs as well as their general consequences. As an example, we discuss the GIC effects on a North American power grid located in mid-latitude regions during the 13-14 March 1989 extreme geomagnetic storm. That was the most extreme storm that occurred in the space era age.

  20. 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.

  1. Annual and semiannual variations of the geomagnetic field at equatorial locations

    NASA Astrophysics Data System (ADS)

    Campbell, W. H.

    1981-06-01

    The annual and semiannual variations of the quiet-sun year (1965) geomagnetic field are examined using geomagnetic records obtained from observatories located between about 0 and 30 deg N geomagnetic latitude. Three separate contributions are analyzed: (1) the quiet-day midnight level (MDT), (2) the solar-quiet daily variation (Sq), and (3) the quiet-time lunar semidiurnal tidal variation (L). Methods of three recent studies (Campbell, 1980a, 1980b) are used to emphasize the equatorial features, and the differences in the seasonal amplitude and phase changes, obtained from a Fourier analysis of annual and semiannual components in the three orthogonal magnetic-field directions, are illustrated. Conclusions are presented, including: (1) the equatorial MDT variations of the northward and vertical components at quiet periods seem to represent the expected seasonal nighttime magnetospheric distortions, (2) the seasonal equatorial region Sq follows closely the annual and semiannual patterns expected to be caused by ionospheric conductivity and heating variations that give rise to a dynamo current at E-region heights, and (3) the lunar seasonal variations show characteristics of dayside ionospheric electrojet origin.

  2. The QUIET Instrument

    SciTech Connect

    Bischoff, C.; et al.

    2012-07-01

    The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the Cosmic Microwave Background, targeting the imprint of inflationary gravitational waves at large angular scales ({approx}1{sup o}). Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4m side-fed Dragonian telescope. The polarimeters which form the focal planes use a highly compact design based on High Electron Mobility Transistors (HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U, and I in a single module. The 17-element Q-band polarimeter array, with a central frequency of 43.1 GHz, has the best sensitivity (69 {mu}Ks{sup 1/2}) and the lowest instrumental systematic errors ever achieved in this band, contributing to the tensor-to-scalar ratio at r < 0:1. The 84-element W-band polarimeter array has a sensitivity of 87 {mu}Ks{sup 1/2} at a central frequency of 94.5 GHz. It has the lowest systematic errors to date, contributing at r < 0:01. The two arrays together cover multipoles in the range {ell} {approx} 25 -- 975. These are the largest HEMT-based arrays deployed to date. This article describes the design, calibration, performance of, and sources of systematic error for the instrument.

  3. Altitude variations in the thermosphere mass density response to geomagnetic activity during the recent solar minimum

    NASA Astrophysics Data System (ADS)

    Liu, X.; Thayer, J. P.; Burns, A.; Wang, W.; Sutton, E.

    2014-03-01

    Accelerometer data from coplanar orbits of Challenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) satellites were used to study the complex altitude and latitude variations of the thermosphere mass density response to geomagnetic activity during 1-10 December 2008 near 09 LT. Helium number densities near 500 km altitude were extracted from the CHAMP and GRACE measurements and clearly show the presence of a winter hemisphere helium bulge. This recent extreme solar minimum indicates that wintertime helium concentrations exceed NRLMSISE-00 model estimates by 30%-70% during quiet geomagnetic activity after adjusting F10.7 input into MSIS. The perturbation in mass density from quiet to active conditions is found to be less enhanced in the winter hemisphere at the higher GRACE altitudes (25%) than at the lower CHAMP altitudes (60%) and is attributed to dynamic behavior in the helium/oxygen transition. The investigation revealed the maximum storm time density perturbation to occur near the He/O transition region with a much weaker maximum near the O/N2 transition region. The altitude of maximum density perturbation occurs where the perturbation in the weighted pressure scale height is equal and opposite to the perturbation in the weighted mean molecular weight scale height. The altitude structure of density scale height perturbation is significantly influenced by the changes in the molecular weight scale height and can account for 50% of the change in mass density scale height in a region correspondingly close to the He/O transition during the 2008 solar minimum period.

  4. Quiet Supersonic Wind Tunnel Development

    NASA Technical Reports Server (NTRS)

    King, Lyndell S.; Kutler, Paul (Technical Monitor)

    1994-01-01

    The ability to control the extent of laminar flow on swept wings at supersonic speeds may be a critical element in developing the enabling technology for a High Speed Civil Transport (HSCT). Laminar boundary layers are less resistive to forward flight than their turbulent counterparts, thus the farther downstream that transition from laminar to turbulent flow in the wing boundary layer is extended can be of significant economic impact. Due to the complex processes involved experimental studies of boundary layer stability and transition are needed, and these are performed in "quiet" wind tunnels capable of simulating the low-disturbance environment of free flight. At Ames, a wind tunnel has been built to operate at flow conditions which match those of the HSCT laminar flow flight demonstration 'aircraft, the F-16XL, i.e. at a Mach number of 1.6 and a Reynolds number range of 1 to 3 million per foot. This will allow detailed studies of the attachment line and crossflow on the leading edge area of the highly swept wing. Also, use of suction as a means of control of transition due to crossflow and attachment line instabilities can be studied. Topics covered include: test operating conditions required; design requirements to efficiently make use of the existing infrastructure; development of an injector drive system using a small pilot facility; plenum chamber design; use of computational tools for tunnel and model design; and early operational results.

  5. 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.

  6. Quiet powered-lift propulsion

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Latest results of programs exploring new propulsion technology for powered-lift aircraft systems are presented. Topics discussed include results from the 'quiet clean short-haul experimental engine' program and progress reports on the 'quiet short-haul research aircraft' and 'tilt-rotor research aircraft' programs. In addition to these NASA programs, the Air Force AMST YC 14 and YC 15 programs were reviewed.

  7. Nature of the Jurassic Magnetic Quiet Zone

    NASA Astrophysics Data System (ADS)

    Tominaga, Masako; Tivey, Maurice A.; Sager, William W.

    2015-10-01

    The nature of the Jurassic Quiet Zone (JQZ), a region of low-amplitude oceanic magnetic anomalies, has been a long-standing debate with implications for the history and behavior of the Earth's geomagnetic field and plate tectonics. To understand the origin of the JQZ, we studied high-resolution sea surface magnetic anomalies from the Hawaiian magnetic lineations and correlated them with the Japanese magnetic lineations. The comparison shows the following: (i) excellent correlation of anomaly shapes from M29 to M42; (ii) remarkable similarity of anomaly amplitude envelope, which decreases back in time from M19 to M38, with a minimum at M41, then increases back in time from M42; and (iii) refined locations of pre-M25 lineations in the Hawaiian lineation set. Based on these correlations, our study presents evidence of regionally and possibly globally coherent pre-M29 magnetic anomalies in the JQZ and a robust extension of Hawaiian isochrons back to M42 in the Pacific crust.

  8. 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.

  9. Quiet High-Speed Fan

    NASA Technical Reports Server (NTRS)

    Lieber, Lysbeth; Repp, Russ; Weir, Donald S.

    1996-01-01

    A calibration of the acoustic and aerodynamic prediction methods was performed and a baseline fan definition was established and evaluated to support the quiet high speed fan program. A computational fluid dynamic analysis of the NASA QF-12 Fan rotor, using the DAWES flow simulation program was performed to demonstrate and verify the causes of the relatively poor aerodynamic performance observed during the fan test. In addition, the rotor flowfield characteristics were qualitatively compared to the acoustic measurements to identify the key acoustic characteristics of the flow. The V072 turbofan source noise prediction code was used to generate noise predictions for the TFE731-60 fan at three operating conditions and compared to experimental data. V072 results were also used in the Acoustic Radiation Code to generate far field noise for the TFE731-60 nacelle at three speed points for the blade passage tone. A full 3-D viscous flow simulation of the current production TFE731-60 fan rotor was performed with the DAWES flow analysis program. The DAWES analysis was used to estimate the onset of multiple pure tone noise, based on predictions of inlet shock position as a function of the rotor tip speed. Finally, the TFE731-60 fan rotor wake structure predicted by the DAWES program was used to define a redesigned stator with the leading edge configured to minimize the acoustic effects of rotor wake / stator interaction, without appreciably degrading performance.

  10. 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.

  11. The composition, temperature, and density structure of cold ions in the quiet terrestrial plasmasphere: GEOS 1 results

    SciTech Connect

    Farrugia, C.J.; Geiss, J.; Balsiger, H. ); Young, D.T. )

    1989-09-01

    The authors present a comprehensive study of the composition, and the density and temperature distributions of the thermal (energy {le} 110 eV) ion population in the terrestrial plasmasphere under quiet geomagnetic conditions. The data were collected by the Ion Composition Experiment (ICE) on board the European Space Agency's GEOS 1 satellite and cover the period from June 1977 to May 1978. They find typical quiet time proton densities to vary smoothly between {approximately} 10{sup 2} cm{sup {minus}3} (L {approx} 6) and 2 {times} 10{sup 3} cm{sup {minus}3} (L {approx} 3). In the local time sector 1,700-2,200 the equatorial proton concentration obeys an inverse fourth power dependence with dipole L. He{sup +} is a major ionic component in all L ranges investigated. Its concentration relative to H{sup +} is highly variable, ranging from {approximately} 1% to, on occasion, over 100%. The averaged variation of He{sup +} with dipole L in the 1,700-2,200 local time range shows a somewhat more rapid decrease with increasing L than does H{sup +}. The temperature in the quiet plasmasphere are between 4 {times} 10{sup 3} K and 1.5 {times} 10{sup 4} K and generally exhibit a slow increase with L value. The average radial temperature gradient near the equator is {approximately} 0.15 K/km. The main ionic constituents are usually in thermal equilibrium throughout the plasmasphere. Using alternate passes in the same region, they discuss the poststorm recovery of the plasmasphere on L shells > 4 for both H{sup +} and He{sup +}. Data are also presented on the minor ions O{sup +}, O{sup ++}, D{sup +}, and He{sup ++}.

  12. The neutral thermosphere at Arecibo during geomagnetic storms

    SciTech Connect

    Burnside, R.G.; Tepley, C.A.; Sulzer, M.P. ); Fuller-Rowell, T.J. ); Torr, D.G. ); Roble, R.G. )

    1991-02-01

    Over the past five years, simultaneous incoherent scatter and optical observations have been obtained at Arecibo, Puerto Rico, during two major geomagnetic storms. The first storm the authors examine occurred during the World Day campaign of 12-16 January 1988, where on 14 January 1988, Kp values greater than 7 were recorded. An ion-energy balance calculation shows that atomic oxygen densities at a fixed height on 14 January 1988 were about twice as large as they were on the quiet days in this period. Simultaneous radar and Fabry-Perot interferometer observations were used to infer nightime O densities on 14-15 January 1988 that were about twice as large as on adjacent quiet nights. On this night, unusually high westward ion velocities were observed at Arecibo. The Fabry-Perot measurements show that the normal eastward flow of the neutral wind was reversed on this night. The second storm they examine occured on the night of 13-14 July 1985, when Kp values reached only 4+, but the ionosphere and thermosphere responded in a similar manner as they did in January 1988. On the nights of both 13-14 July 1985 and 14-15 January 1988, the electron densities observed at Arecibo were significantly higher than they were on nearby geomagnetically quiet nights. These results indicate that major storm effects in thermospheric winds and composition propagate to low latitudes and have a pronounced effect on the ionospheric structure over Arecibo.

  13. Changing environmental conditions during a geomagnetic reversal: Evidence from trace element and isotope variations on Pleistocene flowstone sequences from Cueva Victoria (SE Spain)

    NASA Astrophysics Data System (ADS)

    Mertz-Kraus, R.; Kocot, Y.; Gibert, L.; Scott, G. R.; Jochum, K. P.

    2011-12-01

    The weakening or non-existence of the Earth's magnetic field during a polarity transition is supposed to influence climatic conditions causing variations in, e.g., rainfall, weathering, or the amount of meteoric water infiltrating soils and rocks. Such variations can be monitored by the proxy record (stable and radiogenic isotope or elemental variations) of laminated carbonate sequences precipitated in caves (flowstones). In this study, a multiproxy approach is applied to flowstone samples from Cueva Victoria (SE Spain) recording the Brunhes-Matuyama reversal at 0.78 Ma (Marine Isotope Stage MIS 19) or less likely the lower Jaramillo polarity transition at 1.075 Ma (MIS 31). Cueva Victoria is paleontologically important because of the large number of fossilized fauna found (55 species). The flowstone forms a characteristic layer in the cave system allowing multiple sampling at different locations within the system to test the reproducablity of the analytically derived proxies. Element concentrations were determined on two flowstone samples, using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) along transects covering the geomagnetic change from reverse to normal. Most of the monitored elements show distinctive variations with the highest concentrations in the interval related to the polarity transition: U concentrations are up to factor of 5 higher in the interval of the transition. Increased U concentrations can be explained by (UO2)2+-enriched percolating waters enhancing the weathering during wetter conditions. About four times higher P concentrations indicate changes in vegetation and soil productivity influencing the supply of P to the cave system. Similar concentration maxima are found for the rare earth elements, but also for other elements such as Fe, Na, Al, and Si. Most of these elements are transported bound on colloids and particles. Higher particle supply to the cave environment points to higher infiltration rates caused by

  14. Ubiquitous quiet-Sun jets

    NASA Astrophysics Data System (ADS)

    Martínez Pillet, V.; Del Toro Iniesta, J. C.; Quintero Noda, C.

    2011-06-01

    Context. IMaX/Sunrise has recently reported the temporal evolution of highly dynamic and strongly Doppler shifted Stokes V signals in the quiet Sun. Aims: We attempt to identify the same quiet-Sun jets in the Hinode spectropolarimeter (SP) data set. Methods: We generate combinations of linear polarization magnetograms with blue- and redshifted far-wing circular polarization magnetograms to allow an easy identification of the quiet-Sun jets. Results: The jets are identified in the Hinode data where both red- and blueshifted cases are often found in pairs. They appear next to regions of transverse fields that exhibit quiet-Sun neutral lines. They also have a clear tendency to occur in the outer boundary of the granules. These regions always display highly displaced and anomalous Stokes V profiles. Conclusions: The quiet Sun is pervaded with jets formed when new field regions emerge at granular scales loaded with horizontal field lines that interact with their surroundings. This interaction is suggestive of some form of reconnection of the involved field lines that generates the observed high speed flows.

  15. 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

  16. The geomagnetic tail

    SciTech Connect

    Birn, J. )

    1991-01-01

    A review is presented of the plasma sheet and lobe regions of the magnetotail, focusing principally on large-scale processes or microprocesses with some large-scale effects. Consideration is given to quiet and average structures, not necessarily related to activity phases, with quasi-steady convection aspects, and with the characteristics of dynamic phases including acceleration mechanisms and single particle aspects. Attention is given to various activity models, average and quiet time properties, properties and effects of magnetospheric convection, dynamics of the magnetotail, and the near tail, substorm current wedge.

  17. 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

  18. Effect of Repeated Exposures on Word Learning in Quiet and Noise

    ERIC Educational Resources Information Center

    Blaiser, Kristina M.; Nelson, Peggy B.; Kohnert, Kathryn

    2015-01-01

    This study examines the impact of repeated exposures on word learning of preschool children with and without hearing loss (HL) in quiet and noise conditions. Participants were 19 children with HL and 17 peers with normal hearing (NH). Children were introduced to 16 words: 8 in quiet and 8 in noise conditions. Production and identification scores…

  19. Effect of Repeated Exposures on Word Learning in Quiet and Noise

    ERIC Educational Resources Information Center

    Blaiser, Kristina M.; Nelson, Peggy B.; Kohnert, Kathryn

    2015-01-01

    This study examines the impact of repeated exposures on word learning of preschool children with and without hearing loss (HL) in quiet and noise conditions. Participants were 19 children with HL and 17 peers with normal hearing (NH). Children were introduced to 16 words: 8 in quiet and 8 in noise conditions. Production and identification scores…

  20. Non-triggered auroral substorms and long-period (1-4 mHz) geomagnetic and auroral luminosity pulsations in the polar cap

    NASA Astrophysics Data System (ADS)

    Yagova, Nadezda; Nosikova, Natalia; Baddeley, Lisa; Kozyreva, Olga; Lorentzen, Dag A.; Pilipenko, Vyacheslav; Johnsen, Magnar G.

    2017-03-01

    A study is undertaken into parameters of the polar auroral and geomagnetic pulsations in the frequency range 1-4 mHz (Pc5/Pi3) during quiet geomagnetic intervals preceding auroral substorms and non-substorm background variations. Special attention is paid to substorms that occur under parameters of the interplanetary magnetic field (IMF) conditions typical for undisturbed days (non-triggered substorms). The spectral parameters of pulsations observed in auroral luminosity as measured by a meridian scanning photometer (Svalbard) in the polar cap and near the polar boundary of the auroral oval are studied and compared with those for the geomagnetic pulsations measured by the magnetometer network IMAGE in the same frequency range. It is found that Pc5/Pi3 power spectral density (PSD) is higher during pre-substorm time intervals than for non-substorm days and that specific variations of pulsation parameters (substorm precursors) occur during the last 2-4 pre-substorm hours.

  1. The Study of the Geomagnetic Variation for Sq current System

    NASA Astrophysics Data System (ADS)

    Zhao, X.; Du, A.

    2012-04-01

    The solar quiet variation (Sq) with a period of 24 hrs is a typical one of the quiet variations. Sq is generally caused by atmospheric tide-dynamo in ionosphere and it is controlled by the electric field, electric conductivity in ionosphere and neutral wind in middle-high altitude atmosphere. In our work, the geomagnetic field data observed by 90 ground-based observatories is used to analyze the local time variation of Sq. Sq is derived from five quiet-day geomagnetic data in every month by the FFT method. According to the pattern of geomagnetic X component in Sq, there is a prenoon-postnoon (before noon and after noon) asymmetry. This asymmetry is obvious in spring, summer and winter. The X component at 12:00-13:00 LT is about 5 nT larger than it at 11:00-12:00 LT. The ratio between the X component of daily variable amplitude and Y component of daily variable amplitude in middle and low (high) latitude regions in summer is greater (smaller) than that in winter. Used the sphere harmonic analysis method, the Sq equivalent current system is obtained. From the pattern of Sq current system, the prenoon-postnoon asymmetry may be caused by the electric field in the high latitude region. This electric field has two effects: the one is that the electric field from high latitude maps to the low latitude region; the other is this electric field penetrate to the middle latitude region directly. The combined action of these two effects makes the prenoon-postnoon asymmetry of Sq. The asymmetry also has an obvious seasonal effect. It may relate to the polar Sq and DP2 in the high latitude region.

  2. Analysis of geomagnetic data and cosmic ray variations in periods of magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Mandrikova, Oksana; Zalyaev, Timur; Solovev, Igor; Shevtsov, Boris

    indent=0.63cm In the present paper we have suggested a model of the geomagnetic field variation, which allows us to present the characteristic variation of the field and local perturbations formed in periods of increased geomagnetic activity. The model is based on wavelets and has the following form: [ f(t)= sum_n c_{j,n} phi_{j,n} + sum_{(j_{dist},n)in I_1} d_{j_{dist},n}Psi_{j_{dist},n}(t) + sum_{(j_{dist},n)in I_2} d_{j_{dist},n}Psi_{j_{dist},n}(t) + e(t) ] where component sum_n c_{j,n} phi_{j,n} presents the characteristic variation; component \\sum_{(j_{dist},n)in I_1} d_{j_{dist},n}Psi_{j_{dist},n}(t) presents weak geomagnetic perturbations; component \\sum_{(j_{dist},n)in I_2} d_{j_{dist},n}Psi_{j_{dist},n}(t) presents strong geomagnetic perturbations; j is the scale; I_1, I_2 are the sets of indices; e(t) is the noise; Psi_j = \\{Psi_{j,n}\\}_{n in Z} is the wavelet basis; phi_j = \\{phi_{j,n}\\}_{n in Z} is the scaling function; c_{j,n}=< f, phi_{j,n} > ,d_{j,n}=< f, Psi_{j,n} >. Using the proposed model we have developed a technique of identifying the characteristic variation of the geomagnetic field (in periods of quiet magnetosphere) and components presenting different conditions of the field in periods of perturbations. The technique can be used for various data registration stations and is useful for studying the dynamics of electric current systems in the magnetosphere, the interaction between such systems, and their spatial and temporal distribution. We have also created special rules for estimating the storminess degree of the geomagnetic field. The suggested theoretical tools allow us to determine time points when geomagnetic perturbations arise and to obtain quantitative estimates of the storminess degree. Furthermore, it is also possible to implement these rules in the automatic mode. The theoretical tools mentioned above are also aimed at developing and improving mathematical tools for estimating and monitoring the condition of the geomagnetic

  3. Looking for Peace and Quiet

    ERIC Educational Resources Information Center

    Palin, Ray

    2014-01-01

    Ray Palin, librarian at Sunapee Middle High School in Sunapee, New Hampshire describes what it takes to make the school library a space for those looking for "peace and quiet." Palin begins this article by noting that much has been written about the advantages associated with the learning commons model of library design, however less has…

  4. Looking for Peace and Quiet

    ERIC Educational Resources Information Center

    Palin, Ray

    2014-01-01

    Ray Palin, librarian at Sunapee Middle High School in Sunapee, New Hampshire describes what it takes to make the school library a space for those looking for "peace and quiet." Palin begins this article by noting that much has been written about the advantages associated with the learning commons model of library design, however less has…

  5. [Biotropic effects of geomagnetic storms and their seasonal variations].

    PubMed

    Kuleshova, V P; Pulinets, S A; Sazanova, E A; Kharchenko, A M

    2001-01-01

    A substantial effect of geomagnetic storms on human health with a confidential probability P = 0.95 was revealed. The quantitative estimates of the biotropic effect are presented. For example, the frequency of occurrence of bursts exceeding the average number of hospitalized patients with mental and cardiovascular diseases during magnetic storms increases approximately 2 times compared with quiet periods (based on the data on 1983-84). The frequency of occurrence of myocardial infarction, angina pectoris, violation of cardial rhythm, acute violation of brain blood circulation during storms increases 2.1; 1.6; 1.6; 1.5 times, respectively compared with magnetically quiet periods (based on the data of 1992-96). A similarity of the seasonal distribution of the magnitude of the biotropic effect is revealed in the case of myocardial infarction and the number of magnetic storms: a maximum in the equinox and a minimum in summer.

  6. Interplanetary field and plasma during initial phase of geomagnetic storms

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  7. Modeling solar proton access to geostationary spacecraft with geomagnetic cutoffs

    NASA Astrophysics Data System (ADS)

    Kress, B. T.; Rodriguez, J. V.; Mazur, J. E.; Engel, M.

    2013-12-01

    Solar energetic particle (SEP) cutoffs at geosynchronous orbit are sensitive to moderate geomagnetic activity and undergo daily variations due to the day-night asymmetry of the magnetosphere. At geosynchronous orbit, cutoff rigidity also has a large directional dependence, with the highest cutoff rigidity corresponding to ions arriving from magnetic east and lowest cutoff rigidity corresponding to ions incident from the west. Consequently, during geomagnetically quiet periods, the SEP flux observed by an eastward facing particle detector is significantly lower than observed by a westward facing particle detector. During geomagnetically disturbed periods the cutoff is suppressed allowing SEPs access well inside of geosynchronous, so that the east-west SEP flux ratio approaches unity. Variations in the east-west SEP flux ratio observed by GOES Energetic Particle Sensors (EPS) have recently been reported by Rodriguez et al. (2010). In NOAA's operational processing of EPS count rates into differential fluxes, the differential flux is treated as isotropic and flat over the energy width of the channel. To compare modeled SEP flux with GOES EPS observations, the anisotropy of the flux over the EPS energy range and field of view must be taken into account. A technique for making direct comparisons between GOES EPS observations and SEP flux modeled using numerically computed geomagnetic cutoffs is presented. Initial results from a comparison between modeled and observed flux during the 6-11 December 2006 SEP event are also presented. The modeled cutoffs reproduce the observed flux variations well but are in general too high.

  8. Testing the magnetotail configuration based on observations of low-altitude isotropic boundaries during quiet times

    NASA Astrophysics Data System (ADS)

    Ilie, R.; Ganushkina, N.; Toth, G.; Dubyagin, S.; Liemohn, M. W.

    2015-12-01

    We investigate the configuration of the geomagnetic field on the nightside magnetosphere during a quiet time interval based on National Oceanic and Atmospheric Administration Polar Orbiting Environment Satellites Medium Energy Proton and Electron Detector (NOAA/POES MEPED) measurements in combination with numerical simulations of the global terrestrial magnetosphere using the Space Weather Modeling Framework. Measurements from the NOAA/POES MEPED low-altitude data sets provide the locations of isotropic boundaries; those are used to extract information regarding the field structure in the source regions in the magnetosphere. In order to evaluate adiabaticity and mapping accuracy, which is mainly controlled by the ratio between the radius of curvature and the particle's Larmor radius, we tested the threshold condition for strong pitch angle scattering based on the MHD magnetic field solution. The magnetic field configuration is represented by the model with high accuracy, as suggested by the high correlation coefficients and very low normalized root-mean-square errors between the observed and the modeled magnetic field. The scattering criterion, based on the values of k=Rcρ ratio at the crossings of magnetic field lines, associated with isotropic boundaries, with the minimum B surface, predicts a critical value of kCR˜33. This means that, in the absence of other scattering mechanisms, the strong pitch angle scattering takes place whenever the Larmor radius is ˜33 times smaller than the radius of curvature of the magnetic field, as predicted by the Space Weather Modeling Framework.

  9. 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.

  10. Thermospheric Response to High-Latitude Energy Sources at Quiet Times

    NASA Astrophysics Data System (ADS)

    Moe, M. M.; Moe, K.

    2004-12-01

    Recent results from the CHAMP/STAR accelerometer measurements of thermospheric neutral density have brought back to our attention the existence of important energy sources at high latitudes during geomagnetically quiet times. These energy sources produce a large dayside high-latitude density bulge which is more prominent than the sub-solar density bulge. Evidence for this persistent density enhancement during quiet times has accumulated over the past 35 years. We discuss the numerous measurements of the density bulge made by accelerometers, mass spectrometers, pressure gauges, and satellite orbital decay, as well as the correlation with airglow and ionospheric observations. The energy source for this region of increased neutral density is the solar wind, after it has passed through the Earth's bow shock and magnetosphere. The region of increased density appears on the dayside of both the northern and southern hemispheres, and has a geometrical shape similar to a lunette. The central portion of the arc of the lunette coincides with the downward projection of the magnetospheric dayside cusp. Consequently, the density bulge is best described in solar-geomagnetic coordinates. The wings of the lunette extend far beyond the footprint of the dayside cusp, and are most likely energized by particles that come from other parts of the magnetosphere. The arc of the lunette is clearly displayed by airglow observations and is matched by ionospheric measurements. The corresponding neutral density bulge is much broader in geomagnetic latitude, as one might expect from the longer time constants of neutral processes. We show a Mercator projection of the global density distribution at an altitude of 400 km at 12 hours GMT as an example of the neutral density distribution produced by both the UV and corpuscular energy sources at geomagnetically quiet times.

  11. [Influence of geomagnetic storms on the balance of autonomic regulatory mechanisms].

    PubMed

    Chichinadze, G; Tvildiani, L; Kvachadze, I; Tarkhan-Mouravi, I

    2005-09-01

    The investigation aimed to evaluate autonomic regulatory mechanisms in practically healthy persons during the geomagnetically quiet periods and during geomagnetic storms. The examinations were conducted among the volunteer young men (n=64) 18-22 years of age. The autonomic function was studied on the basis of the heart rate variability. The geomagnetically quiet periods were considered when the value of the K-index was no more then 2 and a geomagnetic storm was considered when the value of the index was 5 and more. It is ascertained that in the both cases the basic statistical indices of the heart rate were identical. The analysis of R-R intervals spectral power gave the possibility to sort the persons examined into the three different groups. The data obtained allowed to suggest that geomagnetic storms influence human organisms through the vagus centers by means of their excitation. This phenomenon may be considered as a self-regulatory physiologic mechanism of the adaptive character. The analysis of the spectral power of R-R intervals may be considered as a sensitive method for the detection of the magnitolabile persons.

  12. Signature of Hale and Gleissberg solar cycles in the geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Demetrescu, Crisan; Dobrica, Venera

    2008-02-01

    The aa index, designed to describe the geomagnetic activity at global scale, has been shown to have increased in the twentieth century by about 65%. The increase in the case of a corrected aa is about 38%, similar to the ones of the recently introduced interhour variability (IHV) and interdiurnal variability (IDV) indices of geomagnetic activity. In terms of 11-year running averages, there is a long-term similarity between aa, R (the sunspot number), x, y, z, and r (geomagnetic indices designed to characterize the solar quiet daily variation, controlled by the solar UV radiation), and S (the solar irradiance). We show that the variation depicted by 11-year running averages of aa and R (and by consequence also of the other parameters mentioned) results from the superposition of Hale and Gleissberg cycle signatures in the corresponding time series. The IHV and IDV indices are included in the analysis. The two signals have a substantial contribution in R (10-30% and 20-34%, respectively, of the amplitude of the solar cycle 22) and aa (<12-27% and ~30%, respectively, of the corresponding cycle 22 in aa). Characteristics of the two signals in the solar and geomagnetic activity and several implications of the geomagnetic activity and the solar quiet daily variation relationship with various solar outputs at the Hale and Gleissberg timescales are discussed.

  13. 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.

  14. A Quiet Transformation

    ERIC Educational Resources Information Center

    Dierke, James S.

    2012-01-01

    The author's 40 years as an educator have led him to an important insight: stress is crippling the schools. On top of other extreme conditions in schools and on students, there is the pressure to achieve and succeed in a fast-paced, chaotic world. This pervasive stress compromises the physical health, and in turn the cognitive and psychological…

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  16. Tsunami related to solar and geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2016-04-01

    The authors of this study wanted to verify the existence of a correlation between earthquakes of high intensity capable of generating tsunami and variations of solar and Earth's geomagnetic activity. To confirming or not the presence of this kind of correlation, the authors analyzed the conditions of Spaceweather "near Earth" and the characteristics of the Earth's geomagnetic field in the hours that preceded the four earthquakes of high intensity that have generated tsunamis: 1) Japan M9 earthquake occurred on March 11, 2011 at 05:46 UTC; 2) Japan M7.1 earthquake occurred on October 25, 2013 at 17:10 UTC; 3) Chile M8.2 earthquake occurred on April 1, 2014 at 23:46 UTC; 4) Chile M8.3 earthquake occurred on September 16, 2015 at 22:54 UTC. The data relating to the four earthquakes were provided by the United States Geological Survey (USGS). The data on ion density used to realize the correlation study are represented by: solar wind ion density variation detected by ACE (Advanced Composition Explorer) Satellite, in orbit near the L1 Lagrange point, at 1.5 million of km from Earth, in direction of the Sun. The instrument used to perform the measurement of the solar wind ion density is the Electron, Proton, and Alpha Monitor (EPAM) instrument, equipped on the ACE Satellite. To conduct the study, the authors have taken in consideration the variation of the solar wind protons density of three different energy fractions: differential proton flux 1060-1900 keV (p/cm^2-sec-ster-MeV); differential proton flux 761-1220 keV (p/cm^2-sec-ster-MeV); differential proton flux 310-580 keV (p/cm^2-sec-ster-MeV). Geomagnetic activity data were provided by Tromsø Geomagnetic Observatory (TGO), Norway; by Scoresbysund Geomagnetic Observatory (SCO), Greenland, Denmark and by Space Weather Prediction Center of Pushkov Institute of terrestrial magnetism, ionosphere and radio wave propagation (IZMIRAN), Troitsk, Moscow Region. The results of the study, in agreement with what already

  17. The effect of solar-geomagnetic activity during and after admission on survival in patients with acute coronary syndromes

    NASA Astrophysics Data System (ADS)

    Vencloviene, Jone; Babarskiene, Ruta; Milvidaite, Irena; Kubilius, Raimondas; Stasionyte, Jolanta

    2014-08-01

    A number of studies have established the effects of solar-geomagnetic activity on the human cardio-vascular system. It is plausible that the heliophysical conditions existing during and after hospital admission may affect survival in patients with acute coronary syndromes (ACS). We analyzed data from 1,413 ACS patients who were admitted to the Hospital of Kaunas University of Medicine, Lithuania, and who survived for more than 4 days. We evaluated the associations between active-stormy geomagnetic activity (GMA), solar proton events (SPE), and solar flares (SF) that occurred 0-3 days before and after admission, and 2-year survival, based on Cox's proportional-hazards model, controlling for clinical data. After adjustment for clinical variables, active-stormy GMA on the 2nd day after admission was associated with an increased (by 1.58 times) hazard ratio (HR) of cardiovascular death (HR = 1.58, 95 % CI 1.07-2.32). For women, geomagnetic storm (GS) 2 days after SPE occurred 1 day after admission increased the HR by 3.91 times (HR = 3.91, 95 % CI 1.31-11.7); active-stormy GMA during the 2nd-3rd day after admission increased the HR by over 2.5 times (HR = 2.66, 95 % CI 1.40-5.03). In patients aged over 70 years, GS occurring 1 day before or 2 days after admission, increased the HR by 2.5 times, compared to quiet days; GS in conjunction with SF on the previous day, nearly tripled the HR (HR = 3.08, 95 % CI 1.32-7.20). These findings suggest that the heliophysical conditions before or after the admission affect the hazard ratio of lethal outcome; adjusting for clinical variables, these effects were stronger for women and older patients.

  18. The effect of solar-geomagnetic activity during and after admission on survival in patients with acute coronary syndromes.

    PubMed

    Vencloviene, Jone; Babarskiene, Ruta; Milvidaite, Irena; Kubilius, Raimondas; Stasionyte, Jolanta

    2014-08-01

    A number of studies have established the effects of solar-geomagnetic activity on the human cardio-vascular system. It is plausible that the heliophysical conditions existing during and after hospital admission may affect survival in patients with acute coronary syndromes (ACS). We analyzed data from 1,413 ACS patients who were admitted to the Hospital of Kaunas University of Medicine, Lithuania, and who survived for more than 4 days. We evaluated the associations between active-stormy geomagnetic activity (GMA), solar proton events (SPE), and solar flares (SF) that occurred 0-3 days before and after admission, and 2-year survival, based on Cox's proportional-hazards model, controlling for clinical data. After adjustment for clinical variables, active-stormy GMA on the 2nd day after admission was associated with an increased (by 1.58 times) hazard ratio (HR) of cardiovascular death (HR=1.58, 95 % CI 1.07-2.32). For women, geomagnetic storm (GS) 2 days after SPE occurred 1 day after admission increased the HR by 3.91 times (HR=3.91, 95 % CI 1.31-11.7); active-stormy GMA during the 2nd-3rd day after admission increased the HR by over 2.5 times (HR=2.66, 95 % CI 1.40-5.03). In patients aged over 70 years, GS occurring 1 day before or 2 days after admission, increased the HR by 2.5 times, compared to quiet days; GS in conjunction with SF on the previous day, nearly tripled the HR (HR=3.08, 95 % CI 1.32-7.20). These findings suggest that the heliophysical conditions before or after the admission affect the hazard ratio of lethal outcome; adjusting for clinical variables, these effects were stronger for women and older patients.

  19. 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.

  20. The NASA quiet engine program

    NASA Technical Reports Server (NTRS)

    Kramer, J. J.; Montegani, F. J.

    1972-01-01

    Initial studies on the design and testing of the quiet engine are described. The principal noise sources considered in the engine selection were the fan machinery noise and the fan and core jet noise. Nacelle acoustic linings are also mentioned. Fan and engine tests are discussed briefly and results indicate that it is possible to achieve or exceed noise reduction objectives of 15 to 20 PNdb below the levels of 707/DC-8 long-range transport aircraft.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  2. 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.

  3. 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

  4. Quantifying the quiet epidemic

    PubMed Central

    2014-01-01

    During the late 20th century numerical rating scales became central to the diagnosis of dementia and helped transform attitudes about its causes and prevalence. Concentrating largely on the development and use of the Blessed Dementia Scale, I argue that rating scales served professional ends during the 1960s and 1970s. They helped old age psychiatrists establish jurisdiction over conditions such as dementia and present their field as a vital component of the welfare state, where they argued that ‘reliable modes of diagnosis’ were vital to the allocation of resources. I show how these arguments appealed to politicians, funding bodies and patient groups, who agreed that dementia was a distinct disease and claimed research on its causes and prevention should be designated ‘top priority’. But I also show that worries about the replacement of clinical acumen with technical and depersonalized methods, which could conceivably be applied by anyone, led psychiatrists to stress that rating scales had their limits and could be used only by trained experts. PMID:25866448

  5. 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.

  6. 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.

  7. 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.

  8. Modelling of geomagnetic induction in pipelines

    NASA Astrophysics Data System (ADS)

    Trichtchenko, L.; Boteler, D. H.

    2002-07-01

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

  9. The national geomagnetic initiative

    NASA Astrophysics Data System (ADS)

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

  10. 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

  11. Remote Observations of Ion Temperatures in the Quiet Time Magnetosphere

    NASA Technical Reports Server (NTRS)

    Keesee, A. M.; Buzulukova, N.; Goldstein, J.; McComas, D. J.; Scime, E. E.; Spence, H.; Fok, M. C.; Tallaksen, K.

    2011-01-01

    Ion temperature analysis of the first energetic neutral atom images of the quiet -time, extended magnetosphere provides evidence of multiple regions of ion heating. This study confirms the existence of a dawn -dusk asymmetry in ion temperature predicted for quiescent magnetospheric conditions by Spence and Kivelson (1993) and demonstrates that it is an inherent magnetospheric feature.

  12. Remote Observations of Ion Temperatures in the Quiet Time Magnetosphere

    NASA Technical Reports Server (NTRS)

    Keesee, A. M.; Buzulukova, N.; Goldstein, J.; McComas, D. J.; Scime, E. E.; Spence, H.; Fok, M. C.; Tallaksen, K.

    2011-01-01

    Ion temperature analysis of the first energetic neutral atom images of the quiet -time, extended magnetosphere provides evidence of multiple regions of ion heating. This study confirms the existence of a dawn -dusk asymmetry in ion temperature predicted for quiescent magnetospheric conditions by Spence and Kivelson (1993) and demonstrates that it is an inherent magnetospheric feature.

  13. 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.

  14. Lower thermosphere densities of N2, O and Ar under high latitude winter conditions

    NASA Technical Reports Server (NTRS)

    Dickinson, P. H. G.; Vonzahn, U.; Baker, K. D.; Jenkins, D. B.

    1986-01-01

    Measurements of the neutral thermosphere were conducted in northern Scandinavia during the Energy Budget Campaign. These measurements included determinations of N2, O, and Ar densities using rocket-borne experiments. The results obtained in the experiments are presented, taking into account also details regarding the employed experimental methods, and an evaluation of the significance of the data. It is found that there are striking differences in thermospheric distributions of the neutral constituents under different geomagnetic conditions. Under quiet geomagnetic conditions there was reasonable agreement with the United States Standard Atmosphere. The concentrations of N2 and Ar were about 70 percent of the predicted values, while the O concentration was about 2.5 times greater.

  15. 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. 

  16. 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.

  17. Magnetosphere of Earth: Geomagnetic Tail

    NASA Astrophysics Data System (ADS)

    Pulkkinen, T.; Murdin, P.

    2000-11-01

    The geomagnetic tail is an elongated region of the MAGNETOSPHERE OF EARTH extending from the near-Earth space in the antisunward direction. It acts as a giant energy reservoir for the magnetosphere and is therefore an important participant in dynamic processes such as GEOMAGNETIC STORMS and substorms (see MAGNETOSPHERE OF EARTH: SUBSTORMS)....

  18. 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.

  19. 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.

  20. Proterozoic Geomagnetic Field Geometry

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  1. Studying the G condition occurrence in different latitudes under solar minimum: Observation and modeling

    NASA Astrophysics Data System (ADS)

    Polekh, N. M.; Romanova, E. B.; Ratovsky, K. G.; Shi, J. K.; Wang, X.; Wang, G. J.

    2015-08-01

    We analyzed the G condition occurrence, using data of ionospheric vertical sounding from stations Norilsk (69.4°N, 88.1°E), Irkutsk (52.5°N, 104°E) and Hainan (18.3°N, 109.3°E) during the last extreme low solar activity period (2006-2009). In most cases, the three stations registered the G condition in May-August; in Norilsk, however, it was registered in March-April 2008. Under quiet geomagnetic conditions, the longest intervals (up to several hours) during which the G condition was continuously registered were observed in Irkutsk and Norilsk in June-July 2008. In Norilsk, it was registered almost every day in the morning and in the daytime (LT) during these months. We performed theoretical modeling of electron density distribution for the cases when the G condition was registered, taking into account the correction of the neutral atmosphere model. The obtained calculations are in good agreement with observed data. Besides, we showed that variations in thermospheric parameters (density, composition, temperature, and wind velocity) can promote formation of the G condition under quiet geomagnetic conditions during the last extreme low solar activity.

  2. Calibrations and observations with the QUIET radiotelescope

    NASA Astrophysics Data System (ADS)

    Monsalve, Raul

    The Q/U Imaging ExperimenT (QUIET) is a project aiming to measure the predicted B-mode polarization of the Cosmic Microwave Background (CMB) radiation and improve the characterization of the E-mode component. The CMB was generated 380,000 years after the Big Bang during a period known as recombination , once the universe had expanded enough to cool to a temperature of 3,600 K. This relic radiation provides crucial information about the large-scale physical conditions and processes prevailing up to and during that period. The prediction of B-mode polarization arises from cosmological models in which the universe underwent an inflationary phase that occurred 10-35 s after the Big Bang, and lasted 10-32 s. Inflation propagated original quantum fluctuations in space-time to the post-inflationary period in the form of gravitational waves, which produced ripples in space and polarization of the CMB in the form of E- and B-mode patterns. Scalar density perturbations were also propagated by the inflation but derived in the formation of E-modes only. The detection of B-mode polarization would thus provide strong support to the inflationary scenario that considers the existence of primordial gravitational waves. The expected level of this signal is ˜ 10-8 K and its measurement represents an enormous scientific and technical challenge. The QUIET telescope observed the microwave sky with two arrays of polarimeters operating at 43 and 94 GHz. It was located in the Chilean Andes and collected more than 10,000 hours of data between October 2008 and December 2010. The detector elements are based on state-of-the-art Monolithic Microwave Integrated Circuit (MMIC) technology and were designed to provide simultaneous measurements of the Q and U Stokes parameters of the sky, improving the efficiency and sensitivity of the instrument. This thesis describes the design of the QUIET telescope, the observations conducted, and the results of the data analysis. The attention

  3. A Quiet Place for Student Veterans

    ERIC Educational Resources Information Center

    Hollingsworth, Margaret

    2015-01-01

    As electronic gadgets predominate a student's life, there comes a need for silence. A quiet place free of electromagnetic spectrum waves, dirty and stray electricity, and the endless chirps, whistles, beeps, and customized signaling. A quiet place can offer solitude for meditation, inspiration, and spiritual awareness. Student involvement in the…

  4. Studies Highlight Classroom Plight of Quiet Students

    ERIC Educational Resources Information Center

    Sparks, Sarah D.

    2012-01-01

    Educators often look for ways to bring quiet children out of their shells, but emerging research suggests schools can improve academic outcomes for introverted students by reducing the pressure to be outgoing and giving all students a little more time to reflect. A 2011 study found teachers from across K-12 rated hypothetical quiet children as…

  5. A Quiet Place for Student Veterans

    ERIC Educational Resources Information Center

    Hollingsworth, Margaret

    2015-01-01

    As electronic gadgets predominate a student's life, there comes a need for silence. A quiet place free of electromagnetic spectrum waves, dirty and stray electricity, and the endless chirps, whistles, beeps, and customized signaling. A quiet place can offer solitude for meditation, inspiration, and spiritual awareness. Student involvement in the…

  6. Studies Highlight Classroom Plight of Quiet Students

    ERIC Educational Resources Information Center

    Sparks, Sarah D.

    2012-01-01

    Educators often look for ways to bring quiet children out of their shells, but emerging research suggests schools can improve academic outcomes for introverted students by reducing the pressure to be outgoing and giving all students a little more time to reflect. A 2011 study found teachers from across K-12 rated hypothetical quiet children as…

  7. Spherical harmonic representation of the main geomagnetic field for world charting and investigations of some fundamental problems of physics and geophysics

    NASA Technical Reports Server (NTRS)

    Barraclough, D. R.; Hide, R.; Leaton, B. R.; Lowes, F. J.; Malin, S. R. C.; Wilson, R. L. (Principal Investigator)

    1981-01-01

    The data processing of MAGSAT investigator B test tapes and data tapes, and tapes of selected data on 15 magnetically quiet days is reported. The 1980 World Chart spherical model was compared with the MAGSAT (3/80) and MAGSAT vector data were used in the models. An article on modelling the geomagnetic field using satellite data is included.

  8. Alternating light-darkness-influenced human electrocardiographic magnetoreception in association with geomagnetic pulsations.

    PubMed

    Otsuka, K; Oinuma, S; Cornélissen, G; Weydahl, A; Ichimaru, Y; Kobayashi, M; Yano, S; Holmeslet, B; Hansen, T L; Mitsutake, G; Engebretson, M J; Schwartzkopff, O; Halberg, F

    2001-01-01

    December 10, 1998, and November 2, 2000, on 19 clinically healthy subjects, 21 to 54 years of age, in Alta, Norway. A geomagnetic record was obtained from the Auroral Observatory of the University of Tromsø. First, frequency-domain measures of HRV were compared for each person in 24-hour spans of high geomagnetic disturbance versus quiet conditions. Second, cross-spectra between geomagnetic activity and HRV measures were quantified via the squared coherence spectrum using 7-day time series. A 7.5% increase in the 24-hour average of heart rate, HR (P = 0.00020) and a decrease in HRV were documented on days of high geomagnetic disturbance. The decrease in HRV was validated statistically for the 'total frequency', 'TF' endpoint (18.6% decrease, P= 0.00009). The decrease in spectral power was found primarily in the 'circaminutan frequency', 'VLF' (21.9% decrease, P< 0.000001) in conjunction with the 'minutes-to-hours' component, ultra-low-frequency, 'ULF' (15.5% decrease, P= 0.00865) and circadecasecundan 'low frequency', 'LF' (14.2% decrease, P = 0.00187) regions of the spectrum. Power-law scaling of the power spectra did not show any statistically significant difference. It is noteworthy that most of the decrease in HRV, except for the circaminutan (VLF) component, was observed only in the season in which sunshine alternated with darkness (D/L), a finding suggesting a mechanism influenced by the alternation of light and darkness. The hypothesis of a light-dark-influenced magnetoreception was also supported by cross-spectral analysis. Group-averaged coherence at frequencies coincident with the geomagnetic Pc 6 pulsations (with periods ranging from 10 minutes to 5 hours) differed with a statistical significance (P < 0.000001) among the three natural lighting conditions, the association being weaker during UL or D/D than during D/L. By contrast, no statistically significant differences were found in terms of the circadian and circasemidian frequencies in relation to the

  9. 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.

  10. 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

  11. Response of nighttime equatorial and low latitude F-region to the geomagnetic storm of August 18, 2003, in the Brazilian sector

    NASA Astrophysics Data System (ADS)

    Sahai, Y.; Univap Team

    This paper presents an investigation of geomagnetic storm effects in the equatorial and low latitude F-region in the Brazilian sector during the intense geomagnetic storm on 18 August 2003 SSC 14 21 UT on 17 08 Sigma Kp 52 Ap 108 vert Dst vert max 168 at 1600 UT on 18 08 Simultaneous ionospheric sounding measurements from two stations viz Palmas 10 2 o S 48 2 o W dip latitude 5 7 o S and S a o Jos e dos Campos 23 2 o S 45 9 o W dip latitude 17 6 o S Brazil are presented for the nights of 16-17 17-18 18-19 19-20 August 2003 quiet disturbed and recovery phases Both stations are equipped with the Canadian Advanced Digital Ionosonde CADI Quiet and disturbed conditions of the F-region ionosphere are compared using data collected from the two stations The relationship between magnetospheric disturbance and low-latitude ionospheric dynamics and generation of ionospheric irregularities will be discussed The GPS data available from several stations in Rede Brasileira de Monitoramento Cont i nuo de GPS Brazilian Network for Continuous GPS Monitoring are used to obtain the vertical total electron content VTEC and the rate of change of TEC per minute on UT days 18 and 19 August 2003 During the disturbed nights the low latitude station S J Campos showed strong positive phase whereas the near equatorial station Palmas showed strong uplifting of the F-layer Normally during the winter months May to August in the Brazilian sector large-scale ionospheric irregularities in form of plasma

  12. Running quietly reduces ground reaction force and vertical loading rate and alters foot strike technique.

    PubMed

    Phan, Xuan; Grisbrook, Tiffany L; Wernli, Kevin; Stearne, Sarah M; Davey, Paul; Ng, Leo

    2017-08-01

    This study aimed to determine if a quantifiable relationship exists between the peak sound amplitude and peak vertical ground reaction force (vGRF) and vertical loading rate during running. It also investigated whether differences in peak sound amplitude, contact time, lower limb kinematics, kinetics and foot strike technique existed when participants were verbally instructed to run quietly compared to their normal running. A total of 26 males completed running trials for two sound conditions: normal running and quiet running. Simple linear regressions revealed no significant relationships between impact sound and peak vGRF in the normal and quiet conditions and vertical loading rate in the normal condition. t-Tests revealed significant within-subject decreases in peak sound, peak vGRF and vertical loading rate during the quiet compared to the normal running condition. During the normal running condition, 15.4% of participants utilised a non-rearfoot strike technique compared to 76.9% in the quiet condition, which was corroborated by an increased ankle plantarflexion angle at initial contact. This study demonstrated that quieter impact sound is not directly associated with a lower peak vGRF or vertical loading rate. However, given the instructions to run quietly, participants effectively reduced peak impact sound, peak vGRF and vertical loading rate.

  13. 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.

  14. General circulation modeling of the thermosphere-ionosphere during a geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Yiǧit, Erdal; Immel, Thomas; Ridley, Aaron; Frey, Harald U.; Moldwin, Mark

    2016-07-01

    Using a three-dimensional general circulation model (GCM) of the upper atmosphere, we investigate the response of the thermosphere-ionosphere system to the August 2011 major geomagnetic storm. The GCM is driven by measured storm-time input data of the Interplanetary Magnetic Field (IMF), solar activity, and auroral activity. Simulations for quiet steady conditions over the same period are performed as well in order to assess the response of the neutral and plasma parameters to the storm. During the storm, the high-latitude mean ion flows are enhanced by up to ~150%. Overall, the global mean neutral temperature increases by up to 15%, while the maximum thermal response is higher in the winter Southern Hemisphere at high-latitudes than the summer Northern Hemisphere: 40% vs. 20% increase in high-latitude mean temperature, respectively. The global mean Joule heating of the neutral atmosphere increases by more than a factor of three. There are distinct hemispheric differences in the magnitude and morphology of the horizontal ion flows and thermospheric circulation during the different phases of the storm. The thermospheric circulation demonstrates the largest amount of hemispheric differences during the later stages of the storm. Dynamical diagnostics show that advective forcing contributes to hemispheric differences.

  15. Annual and semiannual variations of the geomagnetic field at equatorial locations

    USGS Publications Warehouse

    Campbell, W.H.

    1981-01-01

    For a year of quiet solar-activity level, geomagnetic records from American hemisphere observatories located between about 0?? and 30?? north geomagnetic latitude were used to compare the annual and semiannual variations of the geomagnetic field associated with three separate contributions: (a) the quiet-day midnight level, MDT; (b) the solar-quiet daily variation, Sq; (c) the quiet-time lunar semidiurnal tidal variation, L(12). Four Fourier spectral constituents (24, 12, 8, 6 h periods) of Sq were individually treated. All three orthogonal elements (H, D and Z) were included in the study. The MDT changes show a dominant semiannual variation having a range of about 7 gammas in H and a dominant annual variation in Z having a range of over 8 gammas. These changes seem to be a seasonal response to the nightside distortions by magnetospheric currents. There is a slow decrease in MDT amplitudes with increasing latitude. The Sq changes follow the patterns expected from an equatorial ionospheric dynamo electrojet current system. The dominant seasonal variations occur in H having a range of over 21 gammas for the 24 h period and over 12 gammas for the 12 h period spectral components. The higher-order components are relatively smaller in size. The Sq(H) amplitudes decrease rapidly with increasing latitude. Magnetospheric contributions to the equatorial Sq must be less than a few per cent of the observed magnitude. The L(12) variation shows the ionospheric electrojet features by the dominance of H and the rapid decrease in amplitude with latitude away from the equator. However, the seasonal variation range of over 7 gammas has a maximum in early February and minimum in late June that is not presently explainable by the known ionospheric conductivity and tidal behavior. ?? 1981.

  16. A quiet ego quiets death anxiety: humility as an existential anxiety buffer.

    PubMed

    Kesebir, Pelin

    2014-04-01

    Five studies tested the hypothesis that a quiet ego, as exemplified by humility, would buffer death anxiety. Humility is characterized by a willingness to accept the self and life without comforting illusions, and by low levels of self-focus. As a consequence, it was expected to render mortality thoughts less threatening and less likely to evoke potentially destructive behavior patterns. In line with this reasoning, Study 1 found that people high in humility do not engage in self-serving moral disengagement following mortality reminders, whereas people low in humility do. Study 2 showed that only people low in humility respond to death reminders with increased fear of death, and established that this effect was driven uniquely by humility and not by some other related personality trait. In Study 3, a low sense of psychological entitlement decreased cultural worldview defense in response to death thoughts, whereas a high sense of entitlement tended to increase it. Study 4 demonstrated that priming humility reduces self-reported death anxiety relative to both a baseline and a pride priming condition. Finally, in Study 5, experimentally induced feelings of humility prevented mortality reminders from leading to depleted self-control. As a whole, these findings obtained from relatively diverse Internet samples illustrate that the dark side of death anxiety is brought about by a noisy ego only and not by a quiet ego, revealing self-transcendence as a sturdier, healthier anxiety buffer than self-enhancement. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  17. Solar, geomagnetic and seismic activity

    NASA Astrophysics Data System (ADS)

    Mazzarella, A.; Palumbo, A.

    1988-08-01

    An 11-yr modulation of large Italian earthquakes has been successfully identified and found to be positively linked to sunspot activity. The seismic activity appears to be modulated by the 11-yr sunspot cycle through the coherent variation of geomagnetic activity. It is proposed that the two phenomena are linked by the influence of a magnetostriction process on stresses in the crust. An implication of this model is that geomagnetic storms may directly trigger large earthquakes.

  18. 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.

  19. The response of European Daphnia magna Straus and Australian Daphnia carinata King to changes in geomagnetic field.

    PubMed

    Krylov, Viacheslav V; Bolotovskaya, Irina V; Osipova, Elena A

    2013-03-01

    This study investigates the effects of lifelong exposure to reversed geomagnetic and zero geomagnetic fields (the latter means absence of geomagnetic field) on the life history of Daphnia carinata King from Australia and Daphnia magna Straus from Europe. Considerable deviation in the geomagnetic field from the usual strength, leads to a decrease in daphnia size and life span. Reduced brood sizes and increased body length of neonates are observed in D. magna exposed to unusual magnetic background. The most apparent effects are induced by zero geomagnetic field in both species of Daphnia. A delay in the first reproduction in zero geomagnetic field is observed only in D. magna. No adaptive maternal effects to reversed geomagnetic field are found in a line of D. magna maintained in these magnetic conditions for eight generations. Integrally, the responses of D. magna to unusual geomagnetic conditions are more extensive than that in D. carinata. We suggest that the mechanism of the effects of geomagnetic field reversal on Daphnia may be related to differences in the pattern of distribution of the particles that have a magnetic moment, or to moving charged organic molecules owing to a change in combined outcome and orientation of the geomagnetic field and Earth's gravitational field. The possibility of modulation of self-oscillating processes with changes in geomagnetic field is also discussed.

  20. Local time and cutoff rigidity dependences of storm time increase associated with geomagnetic storms

    SciTech Connect

    Kudo, S.; Wada, M. ); Tanskanen, P. ); Kodama, M. )

    1987-05-01

    The cosmic ray increases due to considerable depressions of cosmic ray cutoff rigidity during large geomagnetic storms are investigated. Data from a worldwide network of cosmic ray neutron monitors are analyzed for 17 geomagnetic storms which occurred in the quiet phase of the solar activity cycle during 1966-1978. As expected from the longitudinal asymmetry of the low-altitude geomagnetic field during large geomagnetic storms, a significant local time dependence of the increment in the cosmic ray during large geomagnetic storms, a significant local time dependence of the increment in the cosmic ray intensity is obtained. It is shown that the maximum phases of the local time dependence occur at around 1800 LT and that the amplitudes of the local time dependence are consistent with presently available theoretical estimates. The dependence of the increment on the cutoff rigidity is obtained for both the local time dependent part and the local time independent part of the storm time increase. The local time independent part, excluding the randomizing local time dependent part, shows a clear-cut dependence on cutoff rigidity which is consistent with theoretical estimates.

  1. Prognostic Analysis of the Tactical Quiet Generator

    SciTech Connect

    Hively, Lee M

    2008-09-01

    The U.S. Army needs prognostic analysis of mission-critical equipment to enable condition-based maintenance before failure. ORNL has developed and patented prognostic technology that quantifies condition change from noisy, multi-channel, time-serial data. This report describes an initial application of ORNL's prognostic technology to the Army's Tactical Quiet Generator (TQG), which is designed to operate continuously at 10 kW. Less-than-full power operation causes unburned fuel to accumulate on internal components, thereby degrading operation and eventually leading to failure. The first objective of this work was identification of easily-acquired, process-indicative data. Two types of appropriate data were identified, namely output-electrical current and voltage, plus tri-axial acceleration (vibration). The second objective of this work was data quality analysis to avoid the garbage-in-garbage-out syndrome. Quality analysis identified more than 10% of the current data as having consecutive values that are constant, or that saturate at an extreme value. Consequently, the electrical data were not analyzed further. The third objective was condition-change analysis to indicate operational stress under non-ideal operation and machine degradation in proportion to the operational stress. Application of ORNL's novel phase-space dissimilarity measures to the vibration power quantified the rising operational stress in direct proportion to the less-than-full-load power. We conclude that ORNL's technology is an excellent candidate to meet the U.S. Army's need for equipment prognostication.

  2. Monitoring of the mass density profile along the 0° geomagnetic longitude during magnetic storms with the use of ground magnetometers.

    NASA Astrophysics Data System (ADS)

    Romanova, N.; Stepanova, M. V.; Kozyreva, O. V.; Pilipenko, V.; Zesta, E.

    2015-12-01

    Ground magnetometers offer a very cheap and robust means of globally monitoring the magnetospheric mass density, by determining the ULF field line resonant frequency. ULF waves are almost always present in near-Earth environment and are generated by the solar wind interaction with the terrestrial magnetosphere. These waves from the magnetopause propagate through the magnetosphere. When they encounter a field line that resonates at the same frequency, coupling to the Alfven field line oscillations occurs and the resonance can be detected on the ground at that particular latitude. There are different methods for determining resonant frequencies from ground ULF waves. the density profiles along the 0° geomagnetic longitude were obtained using both the gradient and the amplitude-phase methods for the analysis of the magnetic field data from the magnetometer arrays: SAMBA (South American Meridional B-field Array), MAGDAS and American Antarctic bases (Palmer, WAIS-D). We compared the density profiles during quiet magnetic conditions and during strong magnetic storms (recovery phase). It is shown that in the recovery phase of strong magnetic storms (Dst <-150 nT) profile of the equatorial mass density varies greatly in comparison with the density distribution in quiet days.

  3. 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.

  4. High-torque quiet gear

    NASA Astrophysics Data System (ADS)

    Moody, Paul E.

    1995-07-01

    A high-torque quiet gear construction consists of an inner hub having a plurality of circumferentially spaced arms extending radially outwardly therefrom, and an outer ring member having a plurality of circumferentially spaced-teeth extending radially inwardly therefrom. The ring member further includes a plurality of gear formations on an outer surface thereof for intermeshing with other gears. The teeth of the ring member are received in spaced relation in corresponding spaces formed between adjacent arms of the hub. An elastomeric member is received in the space formed between the hub and the ring member to form a resilient correction between the arms of the hub and the teeth of the ring member. The side surfaces of the arms and the teeth extend generally parallel to each other and at least partially overlap in a longitudinal direction. The purpose of this configuration is to place the elastomeric member in compression when torque is applied to the hub. Since elastomeric material is relatively incompressible, the result is low shear loads on the adhesive bonds which hold the elastomeric member to both the hub and outer ring member.

  5. NASA's Quiet Aircraft Technology Project

    NASA Technical Reports Server (NTRS)

    Whitfield, Charlotte E.

    2004-01-01

    NASA's Quiet Aircraft Technology Project is developing physics-based understanding, models and concepts to discover and realize technology that will, when implemented, achieve the goals of a reduction of one-half in perceived community noise (relative to 1997) by 2007 and a further one-half in the far term. Noise sources generated by both the engine and the airframe are considered, and the effects of engine/airframe integration are accounted for through the propulsion airframe aeroacoustics element. Assessments of the contribution of individual source noise reductions to the reduction in community noise are developed to guide the work and the development of new tools for evaluation of unconventional aircraft is underway. Life in the real world is taken into account with the development of more accurate airport noise models and flight guidance methodology, and in addition, technology is being developed that will further reduce interior noise at current weight levels or enable the use of lighter-weight structures at current noise levels.

  6. Near field zones of quiet

    NASA Astrophysics Data System (ADS)

    Joseph, P.; Elliott, S. J.; Nelson, P. A.

    1994-05-01

    This paper examines the consequences of driving a single secondary loudspeaker to cancel the pressure due to some primary source at a point in its near field. This simple technique has been applied to the sound field in a highly reverberant room to produce zones of quiet in the vicinity of the loudspeaker, which have diameters that are typically equal to one-tenth of the acoustic wavelength, within which the sound pressure level is attenuated by at least 10 dB. The principal advantage gained with this strategy over other active techniques for controlling the sound field in rooms is that the sound pressure level well away from the control point is largely unaffected, an increase of only a small fraction of one dB being typical. Such a loudspeaker-microphone configuration could be located, for example, in the head rests of cars or aeroplanes, or indeed anywhere where the listener is seated for significant lengths of time and subjected to high ambient noise levels such that auditory comfort may be disturbed.

  7. Georg von Neumayer and geomagnetic research

    NASA Astrophysics Data System (ADS)

    Schröder, W.; Wiederkehr, K.-H.; Schlegel, K.

    2010-12-01

    Neumayer was a prominent figure in the development of geophysics in the 19th century from a scientific as well as from an organisational point of view. In this paper we review and highlight his activities and efforts in geomagnetic research within five different aspects of geomagnetism: regional geomagnetic surveys, geomagnetic work in German naval observatories, geomagnetic investigations during the First Polar Year 1882/83, modifications of the Gaussian theory, and geomagnetic charts. In each field Neumayer was a researcher, a thinker, and a stimulating coordinator.

  8. The Lewis Research Center geomagnetic substorm simulation facility

    NASA Technical Reports Server (NTRS)

    Berkopec, F. D.; Stevens, N. J.; Sturman, J. C.

    1977-01-01

    A simulation facility was established to determine the response of typical spacecraft materials to the geomagnetic substorm environment and to evaluate instrumentation that will be used to monitor spacecraft system response to this environment. Space environment conditions simulated include the thermal-vacuum conditions of space, solar simulation, geomagnetic substorm electron fluxes and energies, and the low energy plasma environment. Measurements for spacecraft material tests include sample currents, sample surface potentials, and the cumulative number of discharges. Discharge transients are measured by means of current probes and oscilloscopes and are verified by a photomultiplier. Details of this facility and typical operating procedures are presented.

  9. 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.

  10. Older Individuals Meeting Medicare Cochlear Implant Candidacy Criteria in Noise but Not in Quiet: Are These Patients Improved by Surgery?

    PubMed

    Mudery, Jordan A; Francis, Ross; McCrary, Hilary; Jacob, Abraham

    2017-02-01

    To investigate postoperative hearing outcomes in older patients who qualified for cochlear implant (CI) by Medicare criteria using AZBio sentence tests performed in noise but not in quiet. Review of patient records. University-based otology/neurotology practice. The senior author performed 136 CI between January 2013 and September 2015. Starting in 2013, CI candidacy evaluation included AZBio sentence tests performed in quiet and noise. For the current study, older patients with preoperative AZBio scores greater than 40% in quiet but less than 40% in noise (+10 or +5 dB signal to noise ratio [SNR]) and follow up >/=6 months were included. Cochlear implantation in one ear. Pre- versus postoperative AZBio sentence test scores. Fifteen patients with an average age of 73 years (range, 59-91) met inclusion criteria. Preoperative AZBio scores for the implanted ear averaged 47% points in quiet and 9% points in noise (+10 or +5 dB SNR). Preoperative bilateral AZBio scores averaged 70% points in quiet and 24% points in noise (+10 or +5 dB SNR). Postoperative AZBio scores for the implanted ear improved an average of 71% points in quiet and 51% points in noise. Postoperative bilateral hearing improved 23% points in quiet and 27% points in noise. All patients undergoing CI candidacy testing should be tested in both quiet and noise conditions. For those who qualify only in noise, our results demonstrate that cochlear implantation typically improves hearing both in quiet and noise.

  11. Quiet Supersonic Technology (QueSST)

    NASA Image and Video Library

    2017-03-02

    Mechanical technician Dan Pitts prepares a scale model of Lockheed Martin's Quiet Supersonic Technology (QueSST) X-plane preliminary design for its first high-speed wind tunnel tests at NASA's Glenn Research Center.

  12. The Effect of Quiet on Hearing

    DTIC Science & Technology

    1975-01-01

    34Biomechanics of Ahi Force Operations," Task 723103, "Effects of Operational Noise On Air Force Personnel," and Work Unit 016, "Auditory Responses to... problem . PURPOSE The purpose of this study was to determine the amount of time in quiet required fi ihe hearing threshold levels of experimental...but were not allowed to sleep . Following the period of quiet, and a signal from the experimenter, the headset was replaced by the subject and postqtiet

  13. 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.

  14. Quiet eye facilitates sensorimotor preprograming and online control of precision aiming in golf putting.

    PubMed

    Causer, Joe; Hayes, Spencer J; Hooper, James M; Bennett, Simon J

    2017-02-01

    An occlusion protocol was used to elucidate the respective roles of preprograming and online control during the quiet eye period of golf putting. Twenty-one novice golfers completed golf putts to 6-ft and 11-ft targets under full vision or with vision occluded on initiation of the backswing. Radial error (RE) was higher, and quiet eye was longer, when putting to the 11-ft versus 6-ft target, and in the occluded versus full vision condition. Quiet eye durations, as well as preprograming, online and dwell durations, were longer in low-RE compared to high-RE trials. The preprograming component of quiet eye was significantly longer in the occluded vision condition, whereas the online and dwell components were significantly longer in the full vision condition. These findings demonstrate an increase in preprograming when vision is occluded. However, this was not sufficient to overcome the need for online visual control during the quiet eye period. These findings suggest the quiet eye period is composed of preprograming and online control elements; however, online visual control of action is critical to performance.

  15. 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.

  16. 49 CFR 222.42 - How does this rule affect Intermediate Quiet Zones and Intermediate Partial Quiet Zones?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... and Intermediate Partial Quiet Zones? 222.42 Section 222.42 Transportation Other Regulations Relating... Horns at Groups of Crossings-Quiet Zones § 222.42 How does this rule affect Intermediate Quiet Zones and..., if the public authority provides Notice of Quiet Zone Continuation, in accordance with § 222.43...

  17. Supersonic quiet-tunnel development for laminar-turbulent transition research

    NASA Technical Reports Server (NTRS)

    Schneider, Steven P.

    1995-01-01

    This grant supported research into quiet-flow supersonic wind-tunnels, between February 1994 and February 1995. Quiet-flow nozzles operate with laminar nozzle-wall boundary layers, in order to provide low-disturbance flow for studies of laminar-turbulent transition under conditions comparable to flight. Major accomplishments include: (1) development of the Purdue Quiet-Flow Ludwieg Tube, (2) computational evaluation of the square nozzle concept for quiet-flow nozzles, and (3) measurement of the presence of early transition on the flat sidewalls of the NASA LaRC Mach 3.5 supersonic low-disturbance tunnel. Since items (1) and (2) are described in the final report for companion grant NAG1-1133, only item (3) is described here. A thesis addressing the development of square nozzles for high-speed, low-disturbance wind tunnels is included as an appendix.

  18. Overview of the Arizona Quiet Pavement Program

    NASA Astrophysics Data System (ADS)

    Donavan, Paul; Scofield, Larry

    2005-09-01

    The Arizona Quiet Pavement Pilot Program (QP3) was initially implemented to reduce highway related traffic noise by overlaying most of the Phoenix metropolitan area Portland cement concrete pavement with a one inch thick asphalt rubber friction coarse. With FHWA support, this program represents the first time that pavement surface type has been allowed as a noise mitigation strategy on federally funded projects. As a condition of using pavement type as a noise mitigation strategy, ADOT developed a ten-year, $3.8 million research program to evaluate the noise reduction performance over time. Historically, pavement surface type was not considered a permanent solution. As a result, the research program was designed to specifically address this issue. Noise performance is being evaluated through three means: (1) conventional roadside testing within the roadway corridor (e.g., far field measurements within the right-of-way) (2) the use of near field measurements, both close proximity (CPX) and sound intensity (SI); and (3) far field measurements obtained beyond the noise barriers within the surrounding neighborhoods. This paper provides an overview of the program development, presents the research conducted to support the decision to overlay the urban freeway, and the status of current research.

  19. 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.

  20. What is a geomagnetic storm?

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  1. Kristian Birkeland's pioneering investigations of geomagnetic disturbances

    NASA Astrophysics Data System (ADS)

    Egeland, A.; Burke, W. J.

    2010-04-01

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

  2. Forbush decreases geomagnetic and atmospheric effects cosmogenic nuclides

    NASA Technical Reports Server (NTRS)

    Flueckiger, E. O.

    1986-01-01

    An overview and synthesis is given of recent developments that have occurred in the areas of Forbush decreases, geomagnetic and atmospheric effects, and cosmogenic nuclides. Experimental evidence has been found for substantial differences in the effects of the various types of interplanetary perturbations on cosmic rays, and for a dependence of these effects on the three-dimensional configuration of the interplanetary medium. In order to fully understand and to be able to simulate the solar cosmic ray particle access to the polar regions of the earth we need accurate models of the magnetospheric magnetic field. These models must include all major magnetospheric current systems (in particular the field aligned currents), and they should represent magnetically quiet time periods as well as different levels of geomagnetic activity. In the evolution of magnetospheric magnetic field models, cosmic ray and magnetospheric physicists should work closely together since cosmic ray measurements are a powerful additional tool in the study of the perturbed magnetosphere. In the field of cosmogenic nuclides, finally, exciting new results and developments follow in rapid succession. Thanks to new techniques and new isotopes the analysis of cosmic ray history has entered into a new dimension.

  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. Keith's early work in geomagnetism

    NASA Astrophysics Data System (ADS)

    Lowes, F. J.

    This paper describes how Runcorn was started on his geophysical career by a chance combination of circumstances, when in 1947 he was given the job of measuring the variation of the geomagnetic field with depth inside the Earth, down British coal mines. It then shows how his interest in the semi-conduction of the lower mantle led to attempts to detect DC earth currents, at first again in mines, but later using discarded trans-Pacific telegraph cables. It ends by briefly discussing the “fifth force” measurements he instigated, which, though not a geomagnetic problem, had many similarities with the original mine experiments.

  5. 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.

  6. What is a geomagnetic storm?

    SciTech Connect

    Gonzales, W.D.; Joselyn, J.A.; Kamide, Y.

    1994-04-01

    The authors present a review of geomagnetic storm research. They examine the interaction of the solar wind with the magnetosphere. They argue that a storm results from the extended interaction of the solar wind/magnetosphere when a strong convection electric field is generated, which is able to perturb the ring current above some threshold level, triggering the event. They touch on interrelationships of the solar wind/magnetosphere/ionosphere as it bears on this problem, and offer ideas for continuing research directions to address the origin of geomagnetic storms.

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

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

  9. Annual Variations of the Geomagnetic Field in the Earth's Polar Regions

    NASA Astrophysics Data System (ADS)

    Ou, Jiaming; Du, Aimin

    2017-04-01

    The annual variations of the geomagnetic field play an important role in the coupling processes between the solar wind, magnetosphere and ionosphere. The annual variation is a well-established feature of the geomagnetic field, and usually is applied for modeling the conductivity of the lower mantle [Parkinson, 1983], and for long-term space weather forecasting [Bartels, 1932; Malin and Mete Isikara, 1976; Gonzalez et al., 1994]. Considerable effort has been devoted toward understanding the causes of the geomagnetic field variations, but the suggested physical mechanisms differ widely. The annual variation is relatively weak in many magnetic indices, but it has a distinct signature in the geomagnetic components. Thus, we use the components for this analysis. The components have a positive peak in northern summer and a negative dip in winter [Vestine, 1954]. Vestine [1954] suggested that the annual variation is caused by an ionospheric dynamo in which electric currents in the ionosphere are generated by meridional winds. The winds blow from north-to-south during northern summer, and south-to-north in northern winter. Malin and Mete Isikara [1976], using near-midnight geomagnetic data, concluded that the annual variation results from a latitudinal movement of the auroral electrojet or the ring current. Stauning [2011] derived of the seasonal variation of the quiet daily variations and examined the influence of the sector structure of the interplanetary magnetic field. Ziegger and Mursula [1998] have suggested a third mechanism: that the cause is related to an asymmetric solar wind speed distribution across the heliographic equator. In this paper, we study the annual variation problem using long-term magnetic observation and ionospheric conductivity. The sunlight incident on the ionosphere will be calculated. Although a global analysis is done, particular focus will be placed on the polar regions. This study covers the interval 1990-2010, and the cause of the well

  10. State anxiety and visual attention: the role of the quiet eye period in aiming to a far target.

    PubMed

    Behan, Michael; Wilson, Mark

    2008-01-15

    In this study, we examined how individuals controlled their gaze behaviour during execution of a far aiming task and whether the functional relationship between perception and action was disrupted by increased anxiety. Twenty participants were trained on a simulated archery task, using a joystick to aim and shoot arrows at the target, and then competed in two counterbalanced experimental conditions designed to manipulate the anxiety they experienced. The specific gaze behaviour measured was the duration of the quiet eye period. As predicted, accuracy was affected by the duration of the quiet eye period, with longer quiet eye periods being associated with better performance. The manipulation of anxiety resulted in reductions in the duration of quiet eye. Our results show that the quiet eye period is sensitive to increases in anxiety and may be a useful index of the efficiency of visual orientation in aiming tasks.

  11. Quiet Sun and its Dynamics as Viewed from the Ground and from Space

    NASA Astrophysics Data System (ADS)

    Tziotziou, K.

    2016-04-01

    Over the last years, state-of-the-art ground-based and/or space-based observations using imaging, spectroscopic and spectropolarimetric instruments, at a wide range of wavelengths, reveal that the quiet Sun, just like active regions, is a highly inhomogeneous and dynamic environment that plays an important role in the dynamics of the entire solar atmosphere. This dynamic quiet Sun is manifested through a number of different types of features and phenomena that occur in a large range of spatial and temporal scales and are nowadays believed to be mostly driven by the local magnetic field and its dynamics. Ground-based observations processed with state-of-the-art, post-processing reconstruction techniques, often combined with simultaneous space-based observations from a variety of instruments on different spacecraft, offer a unique opportunity to investigate and understand the physical conditions of the local plasma, the nature, formation mechanisms and evolution of quiet Sun phenomena and possible interrelationships between quiet Sun phenomena occurring at different heights of the quiet Sun solar atmosphere, from the photosphere and chromosphere to the transition region and low corona. We provide a comprehensive review of our latest understanding of quiet Sun and its dynamics as viewed from the ground and from space and discuss the advantages/disadvantages of ground- and space-based observations and future advents in solar observations with new solar instruments.

  12. Development of quiet-flow supersonic wind tunnels for laminar-turbulent transition research

    NASA Technical Reports Server (NTRS)

    Schneider, Steven P.

    1994-01-01

    This grant supported research into quiet-flow supersonic wind-tunnels, between May 1990 and December 1994. Quiet-flow nozzles operate with laminar nozzle-wall boundary layers, in order to provide low-disturbance flow for studies of laminar-turbulent transition under conditions comparable to flight. Major accomplishments include: (1) the design, fabrication, and performance-evaluation of a new kind of quiet tunnel, a quiet-flow Ludweig tube; (2) the integration of preexisting codes for nozzle design, 2D boundary-layer computation, and transition-estimation into a single user-friendly package for quiet-nozzle design; and (3) the design and preliminary evaluation of supersonic nozzles with square cross-section, as an alternative to conventional quiet-flow nozzles. After a brief summary of (1), a description of (2) is presented. Published work describing (3) is then summarized. The report concludes with a description of recent results for the Tollmien-Schlichting and Gortler instability in one of the square nozzles previously analyzed.

  13. Climate determinism or Geomagnetic determinism?

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  14. 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.

  15. Spatial and Temporal Variations of Solar Quiet Daily Sq Variation and Equatorial Electrojet Over Africa: Results From International Heliophysical Year

    NASA Astrophysics Data System (ADS)

    Rabiu, A.; Yumoto, K.; Bello, O.

    2010-12-01

    Space Environment Research Centre of Kyushu University, Japan, installed 13 units of Magnetic Data Acquisition Systems MAGDAS over Africa during the International Heliophysical Year IHY. Magnetic records from 10 stations along the African 96o Magnetic Meridian (Geographical 30o - 40o East) were examined for Solar quiet daily Sq variation in the three geomagnetic field components H, D and Z. Spatial variations of Sq in the geomagnetic components were examined. Signatures of equatorial electrojet and worldwide Sq were identified and studied in detail. H field experienced more variation within the equatorial electrojet zone. Diurnal and seasonal variations of the geomagnetic variations in the three components were discussed. Levels of inter-relationships between the Sq and its variability in the three components were statistically derived and interpreted in line with the mechanisms responsible for the variations of the geomagnetic field. Data from 2 magnetic observatories within equatorial electrojet EEJ strip and 2 stations outside the EEJ strip were employed to evaluate and study the signatures of the Equatorial electrojet over the African sector. The transient variations of the EEJ at two almost parallel axes using Lagos-Ilorin and Nairobi-Addis pairs were examined. The EEJ appear stronger in East than West Africa. The magnitudes and patterns of variation of EEJ strength along the two axes were examined for any simultaneity or otherwise of responses to ionospheric processes. The flow gradient of EEJ along the African sector was estimated and its diurnal variation studied.

  16. 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.

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

    USGS Publications Warehouse

    Campbell, W.H.

    1977-01-01

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

  18. Modelling geomagnetically induced currents in midlatitude Central Europe using a thin-sheet approach

    NASA Astrophysics Data System (ADS)

    Bailey, Rachel L.; Halbedl, Thomas S.; Schattauer, Ingrid; Römer, Alexander; Achleitner, Georg; Beggan, Ciaran D.; Wesztergom, Viktor; Egli, Ramon; Leonhardt, Roman

    2017-06-01

    Geomagnetically induced currents (GICs) in power systems, which can lead to transformer damage over the short and the long term, are a result of space weather events and geomagnetic variations. For a long time, only high-latitude areas were considered to be at risk from these currents, but recent studies show that considerable GICs also appear in midlatitude and equatorial countries. In this paper, we present initial results from a GIC model using a thin-sheet approach with detailed surface and subsurface conductivity models to compute the induced geoelectric field. The results are compared to measurements of direct currents in a transformer neutral and show very good agreement for short-period variations such as geomagnetic storms. Long-period signals such as quiet-day diurnal variations are not represented accurately, and we examine the cause of this misfit. The modelling of GICs from regionally varying geoelectric fields is discussed and shown to be an important factor contributing to overall model accuracy. We demonstrate that the Austrian power grid is susceptible to large GICs in the range of tens of amperes, particularly from strong geomagnetic variations in the east-west direction.

  19. Geomagnetic storms: association with incidence of depression as measured by hospital admission.

    PubMed

    Kay, R W

    1994-03-01

    The hypothesis that geomagnetic storms may partly account for the seasonal variation in the incidence of depression, by acting as a precipitant of depressive illness in susceptible individuals, is supported by a statistically significant 36.2% increase in male hospital admissions with a diagnosis of depressed phase, manic-depressive illness in the second week following such storms compared with geomagnetically quiet control periods. There is a smaller but not statistically significant increase in female psychotic depression and non-psychotic depression admissions following storms. There was no correlation between geomagnetic storm levels and number of male admissions with psychotic depression, which is consistent with a threshold event affecting predisposed individuals. Phase advance in pineal circadian rhythms of melatonin synthesis may be a possible mechanism of causation or be present as a consequence of 5-hydroxytryptamine and adrenergic system dysfunction associated with geomagnetic disturbance. Effects on cell membrane permeability, calcium channel activity and retinal magneto-receptors are suggested as possible underlying biochemical mechanisms.

  20. 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.

  1. 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.

  2. 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.

  3. Multiwavelength analysis of a solar quiet region

    NASA Astrophysics Data System (ADS)

    Tsiropoula, G.; Tziotziou, K.; Schwartz, P.; Heinzel, P.

    2009-01-01

    Context: We examine oscillatory phenomena in a solar network region from multi-wavelength observations obtained by the ground-based Dutch Open Telescope (DOT) and by the Coronal Diagnostic Spectrometer (CDS) on the spacecraft Solar and Heliospheric Observatory (SoHO). The observations were obtained during a coordinated observing campaign in October 2005. Aims: We investigate the temporal variations of the intensities and the velocities in two distinct regions of the quiet Sun, one containing several dark mottles and the other several bright points defining the network boundaries (NB). The aim is to find similarities and/or differences in the oscillatory phenomena observed in these two regions and in different spectral lines formed from the chromosphere to the transition region, as well as the propagation characteristics of waves. Methods: Intensity and velocity variations are studied with wavelet and phase difference analyses. Results: Both regions (i.e. mottles and NB) show a periodicity of ~5 min in all considered lines. The V-V phase differences in the NB region point to an upward propagation of waves; in the region of mottles, for periods of 250-400 s, the phase difference is mainly negative, which suggests a downward propagation, in turn indicating a refraction of waves from the inclined magnetic field of mottles along the line-of-sight. Conclusions: The phase differences at the NB arise from a predominance of upward propagating waves. In the mottles' region, the negative phase differences we found suggest that propagating waves encounter a boundary and are refracted and reflected. Of course, several limitations exist in the exact interpretation of the phase differences, e.g. the complex topology of the magnetic field, the formation conditions and heights of the examined spectral lines, and the low spatial resolution.

  4. Sonic Inlet for the Quiet Engine Program

    NASA Image and Video Library

    1974-01-21

    Brent Miller, of the V/STOL and Noise Division at the National Aeronautics and Space Administration (NASA) Lewis Research Center, poses with a sonic inlet for the NASA Quiet Engine Program. NASA Lewis had first investigated methods for reducing aircraft engine noise in the mid-1950s. Those efforts were resurrected and expanded in the late 1960s. The researchers found that the use of a sonic, or high-throat-Mach-number, inlet was effective at reducing the noise from the engine inlet. The device accelerated the inlet air to near-sonic speeds which kept the forward moving sound waves away from the inlet. The device also deflected the sound waves into the wall to further reduce the noise. NASA Lewis researchers tested models of the sonic inlet in their 9- by 15-Foot Low Speed Wind Tunnel. They found that the general level of aerodynamic performance was good. The tests during simulated takeoff and landing conditions demonstrated the sonic inlet’s ability to provide good aerodynamic and acoustic performance The researchers then successfully tested two full-scale sonic inlet designs, one from Pratt and Whitney and one from General Electric, with fans. A full-scale engine was installed on a thrust stand to determine the sonic inlet’s effect on the engine’s performance. The amount of noise reduction increased as the inlet flow velocity increased, but the full-scale tests did not produce as great a decrease in noise as the earlier small-scale tests.

  5. 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

  6. 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.

  7. Hemispheric differences in the response of the upper atmosphere to the August 2011 geomagnetic storm: A simulation study

    NASA Astrophysics Data System (ADS)

    Yiğit, Erdal; Frey, Harald U.; Moldwin, Mark B.; Immel, Thomas J.; Ridley, Aaron J.

    2016-04-01

    Using a three-dimensional nonhydrostatic general circulation model, we investigate the response of the thermosphere-ionosphere system to the 5-6 August 2011 major geomagnetic storm. The model is driven by measured storm-time input data of the Interplanetary Magnetic Field (IMF), solar activity, and auroral activity. Simulations for quiet steady conditions over the same period are performed as well in order to assess the response of the neutral and plasma parameters to the storm. During the storm, the high-latitude mean ion flows are enhanced by up to 150-180%. Largest ion flows are found in the main phase of the storm. Overall, the global mean neutral temperature increases by up to 15%, while the maximum thermal response is higher in the winter Southern Hemisphere at high-latitudes than the summer Northern Hemisphere: 40% vs. 20% increase in high-latitude mean temperature, respectively. The global mean Joule heating increases by more than a factor of three. There are distinct hemispheric differences in the magnitude and morphology of the horizontal ion flows and thermospheric flows during the different phases of the storm. The largest hemispheric difference in the thermospheric circulation is found during the main and recovery phases of the storm, demonstrating appreciable geographical variations. The advective forcing is found to contribute to the modeled hemispheric differences.

  8. New insights on geomagnetic storms from observations and modeling

    SciTech Connect

    Jordanova, Vania K

    2009-01-01

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

  9. 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

  10. Worldwide Geomagnetic Data Collection and Management

    NASA Astrophysics Data System (ADS)

    Mandea, Mioara; Papitashvili, Vladimir

    2009-11-01

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

  11. Magnetospheric convection during quiet or moderately disturbed times

    NASA Technical Reports Server (NTRS)

    Caudal, G.; Blanc, M.

    1988-01-01

    The processes which contribute to the large-scale plasma circulation in the earth's environment during quiet times, or during reasonable stable magnetic conditions are reviewed. The various sources of field-aligned current generation in the solar wind and the magnetosphere are presented. The generation of field-aligned currents on open field lines connected to either polar cap and the generation of closed field lines of the inner magnetosphere are examined. Consideration is given to the hypothesis of Caudal (1987) that loss processes of trapped particles are competing with adiabatic motions in the generation of field-aligned currents in the inner magnetosphere.

  12. Fine structure of the 2003 geomagnetic jerk near China

    NASA Astrophysics Data System (ADS)

    Ou, J.; Du, A.

    2015-12-01

    The 2003 jerk has an abrupt change in the geomagnetic secular variation (SV), and was recognized as a local phenomenon of internal origin from the satellite observations (Olsen and Mandea, 2007). Notable strength of the 2003 jerk is located near China. The temporal and spatial features at this area are important to resolve the Earth's core fluid flow dynamics at local scale (e.g. Wardinski et al., 2008). We investigate the temporal-spatial development of the 2003 jerk in more detail near China with the ground-based observations and CHAOS-3 core field model. We select the data in the international geomagnetic quiet days to calculate the monthly means. In order to reduce the influence of the external field, we adopt a function comprising the terms associated with the indices of the geomagnetic activity, and the terms of the periodic signals on the observatory monthly means data (Stewart and Whaler, 1992). We then use an empirical AR-2 model to represent the internal field signals in the observatory data. The extreme detection is applied to identify the jerk in the SV time series. The onset time and the strength of the 2003 jerk are obtained through the detection for geomagnetic field component, X, Y and Z. The maximum of the strength of the 2003 jerk is located under the Indian mainland. The onset time of this jerk propagates approximately southeastward. Two jerks in 2001 and 2003 for the Z component are further compared and they are confirmed as independent processes. We suggest the jerk in 2001 identical to the well known 1999 jerk in Europe (Mandea et al., 2000). Our results reveal the fine structures of the 2003 jerk that corroborate the conclusions in previous studies. The larger scale time-spatial structure given by the AR-2 model constructed from ground observatory data (monthly values) is consistent with the results from the CHAOS-3 model. This structure can be applied for further inversion of the local core surface fluid flow motions.

  13. 76 FR 64353 - Buy Quiet Workshop

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-18

    ... HUMAN SERVICES Centers for Disease Control and Prevention Buy Quiet Workshop AGENCY: National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and Prevention (CDC... Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and Prevention (CDC...

  14. 47 CFR 1.924 - Quiet zones.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... impact on the operations of radio astronomy or other facilities that are highly sensitive to interference. Consent throughout this paragraph means written consent from the quiet zone, radio astronomy, research... Radio Astronomy Observatory site located at Green Bank, Pocahontas County, West Virginia, and at the...

  15. 47 CFR 1.924 - Quiet zones.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... impact on the operations of radio astronomy or other facilities that are highly sensitive to interference. Consent throughout this paragraph means written consent from the quiet zone, radio astronomy, research... Radio Astronomy Observatory site located at Green Bank, Pocahontas County, West Virginia, and at the...

  16. Reconnection brightenings in the quiet solar photosphere

    NASA Astrophysics Data System (ADS)

    Rouppe van der Voort, Luc H. M.; Rutten, Robert J.; Vissers, Gregal J. M.

    2016-08-01

    We describe a new quiet-Sun phenomenon which we call quiet-Sun Ellerman-like brightenings (QSEB). QSEBs are similar to Ellerman bombs (EB) in some respects but differ significantly in others. EBs are transient brightenings of the wings of the Balmer Hα line that mark strong-field photospheric reconnection in complex active regions. QSEBs are similar but smaller and less intense Balmer-wing brightenings that occur in quiet areas away from active regions. In the Hα wing, we measure typical lengths of less than 0.5 arcsec, widths of 0.23 arcsec, and lifetimes of less than a minute. We discovered them using high-quality Hα imaging spectrometry from the Swedish 1-m Solar Telescope (SST) and show that, in lesser-quality data, they cannot be distinguished from more ubiquitous facular brightenings, nor in the UV diagnostics currently available from space platforms. We add evidence from concurrent SST spectropolarimetry that QSEBs also mark photospheric reconnection events, but in quiet regions on the solar surface. The movies are available in electronic form at http://www.aanda.org

  17. Variability of the pitch angle distribution of radiation belt ultrarelativistic electrons during and following intense geomagnetic storms: Van Allen Probes observations

    NASA Astrophysics Data System (ADS)

    Ni, Binbin; Zou, Zhengyang; Gu, Xudong; Zhou, Chen; Thorne, Richard M.; Bortnik, Jacob; Shi, Run; Zhao, Zhengyu; Baker, Daniel N.; Kanekal, Shrikhanth G.; Spence, Harlan E.; Reeves, Geoffrey D.; Li, Xinlin

    2015-06-01

    Fifteen months of pitch angle resolved Van Allen Probes Relativistic Electron-Proton Telescope (REPT) measurements of differential electron flux are analyzed to investigate the characteristic variability of the pitch angle distribution of radiation belt ultrarelativistic (>2 MeV) electrons during storm conditions and during the long-term poststorm decay. By modeling the ultrarelativistic electron pitch angle distribution as sinnα, where α is the equatorial pitch angle, we examine the spatiotemporal variations of the n value. The results show that, in general, n values increase with the level of geomagnetic activity. In principle, ultrarelativistic electrons respond to geomagnetic storms by becoming more peaked at 90° pitch angle with n values of 2-3 as a supportive signature of chorus acceleration outside the plasmasphere. High n values also exist inside the plasmasphere, being localized adjacent to the plasmapause and exhibiting energy dependence, which suggests a significant contribution from electromagnetic ion cyclotron (EMIC) wave scattering. During quiet periods, n values generally evolve to become small, i.e., 0-1. The slow and long-term decays of the ultrarelativistic electrons after geomagnetic storms, while prominent, produce energy and L-shell-dependent decay time scales in association with the solar and geomagnetic activity and wave-particle interaction processes. At lower L shells inside the plasmasphere, the decay time scales τd for electrons at REPT energies are generally larger, varying from tens of days to hundreds of days, which can be mainly attributed to the combined effect of hiss-induced pitch angle scattering and inward radial diffusion. As L shell increases to L~3.5, a narrow region exists (with a width of ~0.5 L), where the observed ultrarelativistic electrons decay fastest, possibly resulting from efficient EMIC wave scattering. As L shell continues to increase, τd generally becomes larger again, indicating an overall slower loss

  18. 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.

  19. 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.

  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. 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.

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

    PubMed

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

    2007-02-01

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

  3. [The effects of geomagnetic storms on proteinase and glycosidase activities in fish intestinal mucosa].

    PubMed

    Kuz'mina, V V; Ushakova, N V; Krylov, V V; Petrov, D V

    2014-01-01

    It has been demonstrated that the glycosidase activity of cyprinoid fishes (carp and crucian carp) exposed to a geomagnetic storm for up to 20 h considerably decreases; however, the proteinase activity is weakly altered (a statistically significant decrease in the enzyme activity has been observed only in fasting fish). An in vitro study of the effects of individual half hour intervals of the geomagnetic storm that correspond to the main and recovery phases on the same enzyme activities demonstrates the opposite trend. Independently of the experimental conditions, geomagnetic storms have been shown to influence the enzyme system of fasting fish negatively.

  4. The role of periodicity in perceiving speech in quiet and in background noise.

    PubMed

    Steinmetzger, Kurt; Rosen, Stuart

    2015-12-01

    The ability of normal-hearing listeners to perceive sentences in quiet and in background noise was investigated in a variety of conditions mixing the presence and absence of periodicity (i.e., voicing) in both target and masker. Experiment 1 showed that in quiet, aperiodic noise-vocoded speech and speech with a natural amount of periodicity were equally intelligible, while fully periodic speech was much harder to understand. In Experiments 2 and 3, speech reception thresholds for these targets were measured in the presence of four different maskers: speech-shaped noise, harmonic complexes with a dynamically varying F0 contour, and 10 Hz amplitude-modulated versions of both. For experiment 2, results of experiment 1 were used to identify conditions with equal intelligibility in quiet, while in experiment 3 target intelligibility in quiet was near ceiling. In the presence of a masker, periodicity in the target speech mattered little, but listeners strongly benefited from periodicity in the masker. Substantial fluctuating-masker benefits required the target speech to be almost perfectly intelligible in quiet. In summary, results suggest that the ability to exploit periodicity cues may be an even more important factor when attempting to understand speech embedded in noise than the ability to benefit from masker fluctuations.

  5. 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.

  6. Application of Chinese Geomagnetic Survey and Geomagnetic Model for 2005-2010

    NASA Astrophysics Data System (ADS)

    Xu, R.; Gu, Z.; Yuan, J.

    2016-12-01

    In order to compile geomagnetic map of China, geomagnetic three component survey (including the geomagnetic declination , the inclination and the total intensity ) and the research of geomagnetic model calculation have been carried out in China since 2002. At the same time, geomagnetic map of China for 2005.0 and 2010.0 were finished respectively. Relying on geomagnetic map of China for 2005.0 and 2010.0, seismological and geomagnetic surveillance zones were established in North-South seismic belt and North China, and the new model of geomagnetic three component survey is used in research of earthquake precursor and monitoring. In this paper, the survey model of geomagnetic map, the method of model calculation, compilation geomagnetic map of China and seismo-magnetic research results in seismological and geomagnetic surveillance zone are introduced in detail. Basing on the research results of recent earthquake cases in seismological and geomagnetic surveillance zone, some conclusions have been drawn as follows: the information of seismo-magnetic precursor is reflected by not only the total intensity but also other geomagnetic elements, such as the geomagnetic declination and horizontal component . The model of geomagnetic three component survey, which overcomes the limitations of traditional total intensity monitoring model, helps to increase the amount of information, expand research space and enhance the capabilities of geomagnetic monitoring. Meanwhile, this model has unique advantages in the medium and long term earthquake prediction, especially for forecasting localities of potential of earthquakes. The mode is also an effective method of earthquake monitoring and prediction, which is well worth exploring.

  7. 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

  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. 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.

  10. On the digital geomagnetic observatory at Lunping, Taiwan

    NASA Astrophysics Data System (ADS)

    Huang, Yinn-Nien

    A permanent Lunping Observatory was established by the author in 1965 at Lunping (25°00' N; 121°10' E), Taiwan. A set of Ruska magnetographs, a proton precession magnetometer and a GSI 1st Order Precession Magnetometer have been used to measure the hourly mean values of the geomagnetic three components, H, Z, D, and to determine the three hourly geomagnetic K indices from the daily magnetograms. The purpose of this paper is to show how a set of fluxgate digital magnetometers has been introduced at Lunping Geomagnetic Observatory to automate the routine work of the observatory to save the time spent for the tedious routine manual data production. To maintain the fluxgate digital magnetometers at their best conditions, it has been found that the temperatures of the sensors as well as the electronic parts of the fluxgate magnetometers have to be kept constant. Even though these temperatures have been kept constant, the aging effects of the sensors and electronic parts require absolute measurements of the geomagnetic field to obtain the accurate baseline values of the fluxgate magnetometers. The computer assisted determination of K indices is also presented and discussed.

  11. 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).

  12. 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).

  13. 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

  14. 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.

  15. Geomagnetic Field Reversals and Life on the Earth in Phanerozoic Time

    NASA Astrophysics Data System (ADS)

    Pechersky, D. M.

    2014-10-01

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

  16. Geomagnetic response to solar and interplanetary disturbances

    NASA Astrophysics Data System (ADS)

    Saiz, Elena; Cerrato, Yolanda; Cid, Consuelo; Dobrica, Venera; Hejda, Pavel; Nenovski, Petko; Stauning, Peter; Bochnicek, Josef; Danov, Dimitar; Demetrescu, Crisan; Gonzalez, Walter D.; Maris, Georgeta; Teodosiev, Dimitar; Valach, Fridich

    2013-07-01

    The space weather discipline involves different physical scenarios, which are characterised by very different physical conditions, ranging from the Sun to the terrestrial magnetosphere and ionosphere. Thanks to the great modelling effort made during the last years, a few Sun-to-ionosphere/thermosphere physics-based numerical codes have been developed. However, the success of the prediction is still far from achieving the desirable results and much more progress is needed. Some aspects involved in this progress concern both the technical progress (developing and validating tools to forecast, selecting the optimal parameters as inputs for the tools, improving accuracy in prediction with short lead time, etc.) and the scientific development, i.e., deeper understanding of the energy transfer process from the solar wind to the coupled magnetosphere-ionosphere-thermosphere system. The purpose of this paper is to collect the most relevant results related to these topics obtained during the COST Action ES0803. In an end-to-end forecasting scheme that uses an artificial neural network, we show that the forecasting results improve when gathering certain parameters, such as X-ray solar flares, Type II and/or Type IV radio emission and solar energetic particles enhancements as inputs for the algorithm. Regarding the solar wind-magnetosphere-ionosphere interaction topic, the geomagnetic responses at high and low latitudes are considered separately. At low latitudes, we present new insights into temporal evolution of the ring current, as seen by Burton's equation, in both main and recovery phases of the storm. At high latitudes, the PCC index appears as an achievement in modelling the coupling between the upper atmosphere and the solar wind, with a great potential for forecasting purposes. We also address the important role of small-scale field-aligned currents in Joule heating of the ionosphere even under non-disturbed conditions. Our scientific results in the framework of the

  17. 49 CFR 222.35 - What are the minimum requirements for quiet zones?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Quiet Zone. (iii) New Quiet Zones and New Partial Quiet Zones established along the same rail line... requirements applicable to New Quiet Zones and New Partial Quiet Zones. (iii) The deletion of any public... 49 Transportation 4 2012-10-01 2012-10-01 false What are the minimum requirements for quiet...

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

    PubMed Central

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

    2008-01-01

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

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

    PubMed

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

    2005-10-01

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

  20. 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

  1. Improvement of Quiet Standing Balance in Patients with Wallenberg Syndrome after Rehabilitation

    PubMed Central

    Na, Eun Hye; Han, Soo Jeong

    2011-01-01

    Objective To evaluate quiet standing balance of patients with Wallenberg syndrome before and after rehabilitation. Method Six patients with Wallenberg syndrome were enrolled within one month after being affected by an infarct of the lateral medulla. Quiet standing balance was assessed using posturography with eyes open and closed. The assessment was repeated after the patients had undergone rehabilitation treatment for three to nine months, and the results of the two assessments were compared. Results The quiet standing balance evaluation was performed by measurement of center of pressure (CoP) movement. In the initial test, the mean scores of mediolateral and anteroposterior speed, velocity movement, mediolateral and anteroposterior extent of CoP were all high, indicating impairments of quiet standing balance in the patients. After rehabilitation treatment, the anteroposterior speed and extent, the mediolateral speed and extent, and velocity moment of CoP showed statistically significant reductions in the eyes open condition (p<0.05), and the anteroposterior speed and extent and velocity moment of CoP had decreased in the eyes closed condition (p<0.05). Mediolateral speed and extent of CoP in the eyes closed condition had also decreased, but the reduction was not statistically significant. Conclusion This study demonstrated improvements of quiet standing balance, especially anteroposterior balance, in patients with Wallenberg syndrome following rehabilitation. We suggest that balance training is important in the rehabilitation of Wallenberg syndrome and that, as an objective measure of balance status, posturography is useful in the assessment of quiet standing balance. PMID:22506207

  2. 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

  3. The Hidden Gifts of Quiet Kids

    ERIC Educational Resources Information Center

    Trierweiler, Hannah

    2006-01-01

    The author relates that she was an introvert child. It has always taken her time and energy to find her place in a group. As a grown-up, she still needed quiet time to regroup during a busy day. In this article, the author presents an interview with Marti Olsen Laney, author of "The Hidden Gifts of the Introverted Child." During the interview,…

  4. Mideast stays quiet but has vigor

    SciTech Connect

    Not Available

    1985-05-01

    New drilling activity in the Middle East comes in the Egyptian Red Sea and at both Yemen and Qatar. The last in the scene of the giant North Dome gas development. Otherwise the Mideast sector is quiet with hard production ceilings demanded by OPEC and a war on the east coast of the gulf causing more confusion. A review of the current activity is presented.

  5. Children's perception of nonnative-accented sentences in noise and quiet.

    PubMed

    Bent, Tessa; Atagi, Eriko

    2015-12-01

    Adult listeners' word recognition is remarkably robust under a variety of adverse listening conditions. However, the combination of two simultaneous listening challenges (e.g., nonnative speaker in noise) can cause significant word recognition decrements. This study investigated how talker-related (native vs nonnative) and environment-related (noise vs quiet) adverse conditions impact children's and adults' word recognition. Five- and six-year-old children and adults identified sentences produced by one native and one nonnative talker in both quiet and noise-added conditions. Children's word recognition declined significantly more than adults' in conditions with one source of listening adversity (i.e., native speaker in noise or nonnative speaker in quiet). Children's performance when the listening challenges were combined (nonnative talker in noise) was particularly poor. Immature speech-in-noise perception may be a result of children's difficulties with signal segregation or selective attention. In contrast, the explanation for children's difficulty in the mapping of unfamiliar pronunciations to known words in quiet listening conditions must rest on children's limited cognitive or linguistic skills and experiences. These results demonstrate that children's word recognition abilities under both environmental- and talker-related adversity are still developing in the early school-age years.

  6. Modeling the quiet time inner plasma sheet protons

    NASA Astrophysics Data System (ADS)

    Wang, Chih-Ping; Lyons, Larry R.; Chen, Margaret W.; Wolf, Richard A.

    2001-04-01

    inner plasma sheet the magnitude of the Hall term in the generalized Ohm's law is not small compared with the quiet time electric field. This suggests that the frozen-in condition E=-v×B is not valid in the inner plasma sheet and that the Hall term needs to be included to obtain an appropriate approximation of the generalized Ohm's law in that region.

  7. The heating of the quiet solar chromosphere

    NASA Technical Reports Server (NTRS)

    Kalkofen, Wolfgang

    1990-01-01

    The quiet solar chromosphere shows three distinct regions. Ordered according to the strength of the emission from the low and middle chromosphere they are (1) the magnetic elements on the boundary of supergranulation cells, (2) the bright points in the cell interior, and (3) the truly quiet chromosphere, also in the cell interior. The magnetic elements on the cell boundary are associated with intense magnetic fields and are heated by waves with very long periods, ranging from six to twelve minutes; the bright points are associated with magnetic elements of low field strength and are heated by (long-period) waves with periods near the acoustic cutoff period of three minutes; and the quiet cell interior, which is free of magnetic field, may be heated by short-period acoustic waves, with periods below one minute. This paper reviews mainly the heating of the bright points and concludes that the large-amplitude, long-period waves heating the bright points dissipate enough energy to account for their chromospheric temperature structure.

  8. BUY QUIET INITIATIVE IN THE USA

    PubMed Central

    Beamer, Bryan; McCleery, Trudi; Hayden, Charles

    2016-01-01

    Noise-induced hearing loss is still considered one of the most common work-related illnesses in the United States of America. The U.S. National Institute for Occupational Safety and Health launched a national Buy Quiet campaign to raise awareness of the importance of purchasing quieter equipment. Buy Quiet encourages companies to seek out and demand quieter equipment thus driving the market to design and create quieter products. In the long run, investment in noise controls should be more prevalent as the market demands quieter products. This paradigm occurs as the market for quieter products expands both from the supply side (manufacturers) and the demand side (tool and equipment purchasers). The key to experiencing the reduced costs and increased benefits of Buy Quiet will be to develop partnerships between manufacturers and consumers. To this end, the U.S. National Institute for Occupational Safety and Health continues to work with partners to educate stakeholders about the risks and true costs of noise-induced hearing loss, as well as the economic benefits of buying quieter equipment. PMID:27274613

  9. BUY QUIET INITIATIVE IN THE USA.

    PubMed

    Beamer, Bryan; McCleery, Trudi; Hayden, Charles

    2016-04-01

    Noise-induced hearing loss is still considered one of the most common work-related illnesses in the United States of America. The U.S. National Institute for Occupational Safety and Health launched a national Buy Quiet campaign to raise awareness of the importance of purchasing quieter equipment. Buy Quiet encourages companies to seek out and demand quieter equipment thus driving the market to design and create quieter products. In the long run, investment in noise controls should be more prevalent as the market demands quieter products. This paradigm occurs as the market for quieter products expands both from the supply side (manufacturers) and the demand side (tool and equipment purchasers). The key to experiencing the reduced costs and increased benefits of Buy Quiet will be to develop partnerships between manufacturers and consumers. To this end, the U.S. National Institute for Occupational Safety and Health continues to work with partners to educate stakeholders about the risks and true costs of noise-induced hearing loss, as well as the economic benefits of buying quieter equipment.

  10. The heating of the quiet solar chromosphere

    NASA Technical Reports Server (NTRS)

    Kalkofen, Wolfgang

    1990-01-01

    The quiet solar chromosphere shows three distinct regions. Ordered according to the strength of the emission from the low and middle chromosphere they are (1) the magnetic elements on the boundary of supergranulation cells, (2) the bright points in the cell interior, and (3) the truly quiet chromosphere, also in the cell interior. The magnetic elements on the cell boundary are associated with intense magnetic fields and are heated by waves with very long periods, ranging from six to twelve minutes; the bright points are associated with magnetic elements of low field strength and are heated by (long-period) waves with periods near the acoustic cutoff period of three minutes; and the quiet cell interior, which is free of magnetic field, may be heated by short-period acoustic waves, with periods below one minute. This paper reviews mainly the heating of the bright points and concludes that the large-amplitude, long-period waves heating the bright points dissipate enough energy to account for their chromospheric temperature structure.

  11. Nanoflare Heating of the Quiet Sun

    NASA Astrophysics Data System (ADS)

    Viall, N. M.; Klimchuk, J. A.

    2015-12-01

    How the solar corona is heated to temperatures of over 1 MK, while the photosphere below is only ~ 6000 K remains one of the outstanding problems in all of space science. Solving this problem is crucial for understanding Sun-Earth connections, and will provide new insight into universal processes such as magnetic reconnection and wave-particle interactions. We use a systematic technique to analyze the properties of coronal heating throughout the solar corona using data taken with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Our technique computes cooling times of the coronal plasma on a pixel-by-pixel basis and has the advantage that it analyzes all of the coronal emission, including the diffuse emission surrounding distinguishable coronal features. We have already applied this technique to 15 different active regions, and find clear evidence for dynamic heating and cooling cycles that are consistent with the 'impulsive nanoflare' scenario. What about the rest of the Solar corona? Whether the quiet Sun is heated in a similar or distinct manner from active regions is a matter of great debate. Here we apply our coronal heating analysis technique to quiet Sun locations. We find areas of quiet Sun locations that also undergo dynamic heating and cooling cycles, consistent with impulsive nanoflares. However, there are important characteristics that are distinct from those of active regions.

  12. Radio-quiet Gamma-ray Pulsars

    NASA Astrophysics Data System (ADS)

    Lin, Lupin Chun-Che

    2016-09-01

    A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog) known samples classified as radio-quiet γ-ray pulsars with radio flux density (S1400) of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on) are also specified to discuss their common and specific features.

  13. New geomagnetic indices as proxies of the energy embedded in the thermosphere-ionosphere system by solar-wind and magnetospheric effects

    NASA Astrophysics Data System (ADS)

    Valette, Jean-Jacques; Lathuillère, Chantal; Mathieu, Pau; Menvielle, Michel; Bruinsma, Sean; Biancale, Richard

    Planetary geomagnetic indices ap are classically used in models to quantify the geomagnetic forcing of the thermosphere/ionosphere system as a consequence of solar wind/magnetosphere coupling. These indices are based upon K indices measured at a non-evenly distributed network of 13 geomagnetic observatories. K indices are directly related to the range during 3-hour intervals of the irregular variations in the horizontal components of the magnetic field. There are accordingly 8 K-derived planetary indices per day, corresponding to UT intervals 00-03, 03-06 up to 21-24. K-indices are proxies of the energy related to the geomagnetic activity. This approach of 3-hour resolution is a strong limitation for precise modelling of the thermosphere/ionosphere response to geomagnetic forcing. We therefore introduce new indices based on another proxy of the magnetic energy, namely the root mean square (rms) of the irregular variations in the magnetic horizontal components. Using such proxy does not put constraints on the length of the time interval over which the indices are derived. From the irregular variations re-computed at each observatory, the new magnetic indices are derived following algorithms similar to those used for am, aa planetary geomagnetic indices derivation. Results from statistical studies of these new indices are presented during quiet, medium or stormy magnetic activity. The potential benefits for specific thermospheric studies or Space Weather applications are discussed.

  14. Tectonic evolution of the Perth Abyssal Plain's Quiet Zone, Southeast Indian Ocean

    NASA Astrophysics Data System (ADS)

    Ehrlich, Zohar Louis; Granot, Roi; Williams, Simon E.

    2013-04-01

    During the Late Jurassic period, the Greater-Indian plate was torn away from Australia, dissociating East Gondwanaland. The Perth Abyssal Plain (PAP) is the southernmost rift segment along the western Australian margin, and has an onset age of ~136 Ma. New marine magnetic and swath bathymetry data, crossing the entire PAP, were acquired recently on geophysical cruise ss2011v06 aboard the R/V Southern Surveyor. These have lead to the outline of conjugate Indian and Australian M-series isochrons in the east and west PAP, respectively [1]. Yet, most of the PAP was created during the Cretaceous Normal Superchron (CNS, 121-83 Ma), a period of no geomagnetic field reversals, hence no comprehensive tectonic model for the PAP exists . Here we present preliminary findings of an analytic bathymetric and magnetic investigation aimed at elucidating the PAP's quiet zone. Recent discoveries regarding the evolution of the geomagnetic field during the CNS [2] provide new time markers that can be utilized to date the oceanic crust. The magnetic anomaly data exhibit the Q2 anomaly marker (~108 Ma), further constraining the spreading history of the PAP. Together with the ridgelet transform method [3] for automated abyssal hill delineation, we present new constraints on the development of crustal construction processes (spreading location, direction and rates) that took place along the PAP spreading center. References: [1] S.E. Williams, J.M. Whittaker, R. Granot, R.D. Muller (in preparation), New constraints on the seafloor spreading history in the Perth Abyssal Plain. [2] Granot, R., J. Dyment, and Y. Gallet (2012), Geomagnetic field variability during the Cretaceous Normal Superchron, Nature Geoscience, 5(3), 220-223. [3] Downey, N. J. and R. W. Clayton (2007), A ridgelet transform method for constraining tectonic models via abyssal-hill morphology, Geochemistry Geophysics Geosystems, 8, Q03004, doi: 10.1029/2006GC001440.

  15. The influence of quiet eye training and pressure on attention and visuo-motor control.

    PubMed

    Vine, Samuel J; Wilson, Mark R

    2011-03-01

    The aim of this study was to examine the efficacy of an intervention designed to train effective visual attentional control (quiet eye-training) for a far aiming skill, and determine whether such training protected against attentional disruptions associated with performing under pressure. Sixteen novice participants wore a mobile eye-tracker to assess their visual attentional control (quiet eye) during the completion of 520 basketball free throws carried out over 8 days. They first performed 40 pre-test free throws and were randomly allocated into a quiet eye (QE) training or Control group (technical instruction only). Participants then performed 360 free throws during a training period and a further 120 test free throws under conditions designed to manipulate the level of anxiety experienced. The QE trained group maintained more effective visual attentional control and performed significantly better in the pressure test compared to the Control group, providing support for the efficacy of attentional training for visuo-motor skills.

  16. Electric utility industry experience with geomagnetic disturbances

    SciTech Connect

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

    1991-09-01

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

  17. Electric utility industry experience with geomagnetic disturbances

    SciTech Connect

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

    1991-09-01

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

  18. [Severe trauma rate during planet geomagnetic storms].

    PubMed

    Kuleshova, V P; Pulinets, S A

    2001-01-01

    The growth of the diurnal frequency of appearance of heavy traumas during planetary geomagnetic storms is shown and statistically justified. No effect of short-term geomagnetic disturbances of natural and technogenic nature on the occurrence of acute mental and cardiovascular pathologies was detected on the basis of diurnal data.

  19. 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.

  20. Structuring of intermediate scale equatorial spread F irregularities during intense geomagnetic storm of solar cycle 24

    NASA Astrophysics Data System (ADS)

    Kakad, B.; Gurram, P.; Tripura Sundari, P. N. B.; Bhattacharyya, A.

    2016-07-01

    Here we examine the structuring of equatorial plasma bubble (EPB) during intense geomagnetic storm of solar cycle (SC) 24 that occurred on 17 March 2015 using spaced receiver scintillation observations on a 251 MHz radio signal, recorded by a network of stations in Indian region. As yet, this is the strongest geomagnetic storm (Dstmin˜-223nT) that occurred in present SC. Present study reveals that the structuring of equatorial spread F (ESF) irregularities was significantly different on 17 March as compared to quiet days of corresponding month. ESF irregularities of intermediate scale (100 m to few kilometers) are observed at unusually higher altitudes (≥ 800 km) covering wider longitudinal-latitudinal belt over Indian region. A presence of large-scale irregularity structures with stronger ΔN at raised F peak with small-scale irregularities at even higher altitudes is observed. It caused strong focusing effect (S4>1) that prevails throughout premidnight hours at dip equatorial station Tirunelveli. Other observational aspect is that zonal irregularity drifts over low-latitude station Kolhapur exhibited a large deviation of ˜230 m/s from their average quiet time pattern. During this geomagnetic storm, two southward turnings of significant strength (BZ≤-15 nT) occurred at 11.4 IST (Indian standard time) and 17.9 IST. The later southward turning of interplanetary magnetic field (IMF)BZ resulted in a large eastward prompt penetration electric field (PPEF) close to sunset hours in Indian longitude. Estimates of PPEF obtained from real-time ionospheric model are too low to explain the observed large upliftment of F region in the post sunset hours. Possible reason for observed enhanced PPEF-linked effects is discussed.

  1. The Quiet Room: A Cyber-Free Haven in the Community Library.

    ERIC Educational Resources Information Center

    Jacob, Bernard; Morphew, Carol

    1997-01-01

    Because community libraries are becoming centers of suburban and "exurban" activity, quiet study rooms are being constructed for customers intent on concentrated study. Discusses functional (size, location, furniture) and physical (acoustic, heating, ventilation, air conditioning, lighting, electronic support) considerations of quiet…

  2. The Quiet Room: A Cyber-Free Haven in the Community Library.

    ERIC Educational Resources Information Center

    Jacob, Bernard; Morphew, Carol

    1997-01-01

    Because community libraries are becoming centers of suburban and "exurban" activity, quiet study rooms are being constructed for customers intent on concentrated study. Discusses functional (size, location, furniture) and physical (acoustic, heating, ventilation, air conditioning, lighting, electronic support) considerations of quiet…

  3. Quiet Eye Duration Is Responsive to Variability of Practice and to the Axis of Target Changes

    ERIC Educational Resources Information Center

    Horn, Robert R.; Okumura, Michelle S.; Alexander, Melissa G. F.; Gardin, Fredrick A.; Sylvester, Curtis T.

    2012-01-01

    We tested the hypothesis that quiet eye, the final fixation before the initiation of a movement in aiming tasks, is used to scale the movement's parameters. Two groups of 12 participants (N = 24) threw darts to targets in the horizontal and vertical axes under conditions of higher (random) or lower (blocked) target variability. Supporting our…

  4. Quiet Eye Duration Is Responsive to Variability of Practice and to the Axis of Target Changes

    ERIC Educational Resources Information Center

    Horn, Robert R.; Okumura, Michelle S.; Alexander, Melissa G. F.; Gardin, Fredrick A.; Sylvester, Curtis T.

    2012-01-01

    We tested the hypothesis that quiet eye, the final fixation before the initiation of a movement in aiming tasks, is used to scale the movement's parameters. Two groups of 12 participants (N = 24) threw darts to targets in the horizontal and vertical axes under conditions of higher (random) or lower (blocked) target variability. Supporting our…

  5. 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.

  6. Changes In Atmosphere and Ionosphere Caused By Solar-geomagnetic Activity, Within Belgrade Area

    NASA Astrophysics Data System (ADS)

    Mitic, M.; Djordjevic, A.; Mihajlovic, S. J.

    Results of the different solar-climatic and terrestrial investigations show mutual con- nection between changes in the solar activity, geomagnetic field and meteorological parameters, such as: temperature, humidity and air pressure. In order to determine the influence of solar-geomagnetic activity on atmosphere and ionosphere within Bel- grade area, characteristic parameters were selected: - temperature T, as the atmosphere parameter; - critical frequency foF2 as the ionosphere parameter; - horisontal com- ponent H, as the geomagnetic field parameter; - Ri, relative Sunspot number, as the parameter of solar activity. Investigation has been done for the period from 1958-1995, which has been taken as the time interval. This period belongs to the descendent branch of the 19-th, 20- th, 21-st and 22-nd solar cycle. Values of the ionosphere parameters were considered for the 21-st cycle (as that data was available to the author). During the observation, mentioned parameters were compared in different ways. Changes were observed as behavior of mid-monthly and mid-yearly values of parameters through specific time intervals, seasons, minimums and maximums of Sun activity. It has been established that the temperature and the horisontal component of geomagnetic field have period of about 22-years and 11-years lasting period for relative Sunspots number Ri. Changes in values of ionosphere parameters were well correlated with changes of horizontal component for quiet days, values of temperature and the Sunspots number, as it was suspected. Further, secular variations were formed for more detailed investigations. The secular variation of values, for any parameter, is presented as a function of change of consec- utive yearly values in a particular time interval. By application of Fourier Transforma- tion, a spectral analysis of secular variations has been done. Changes were separated in duration of 6 and 9 months, 1, 2 and 3.5 years. In order to make a "view" on secular

  7. Day-To Variability of the Quiet-Time Equatorial Electrojet and Post-Sunset Occurrence of Equatorial Ionospheric Scintillations

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Archana; Okpala, Kingsley

    Strength of the equatorial electrojet (EEJ) derived from measurements of the horizontal component H of the geomagnetic field at an equatorial station, Tirunelveli, and a low-latitude station Alibag, outside the influence of the EEJ, on International quiet (IQ) days of the years 2001-2005, have been subjected to Principal Component Analysis to determine the principal components (PCs) that describe the variability of the quiet-time EEJ. It is found that the first three PCs together account for 94% of the variability of the EEJ observed during the IQ days of this period. PC1 itself represents about 64% of the EEJ variations, while PC2 and PC3 respectively account for 23% and 7% of the quiet-time variability of the EEJ during these years when the daily adjusted 10.7 cm solar flux, Sa, decreased from values exceeding 200 to around 100. The temporal structure of PC1 is such that it contributes only to the variability of the normal electrojet and cannot explain events such as the counter-electrojet (CEJ). A model is constructed for quiet-day PC1 scores as a function of day number and solar activity to describe a major part of the variability of the normal quiet-time EEJ. However, the CEJ and other 'abnormal' variations such as an afternoon enhancement of the EEJ, are only associated with PC2 and PC3. The quiet-day PC2 and PC3 scores obtained in this study, therefore, indicate the influence of forcing of the equatorial ionosphere from below. The day-to-day variability of the quiet-time pre-reversal enhancement of the post-sunset equatorial F region zonal electric field, which plays a crucial role in the occurrence of scintillation-producing equatorial ionospheric irregularities, is also influenced by forcing from below. In this context, occurrence of scintillations on a 251 MHz signal, transmitted from a geostationary satellite, and recorded at Tirunelveli, is studied in relation to the PC scores, which describe the variability of the EEJ, in order to identify a possible

  8. 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.

  9. Magnetospheric access of solar particles and the configuration of the distant geomagnetic field, volume 1. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Evans, L. C.

    1972-01-01

    The access of 1.2 to 40 MeV protons and 0.4 to 1.0 MeV electrons from interplanetary space to the polar cap regions was investigated with an experiment on board a low altitude, polar-orbiting satellite (0G0 4). A total of 333 quiet time observations of the electron polar cap boundary give a mapping of the boundary between open and closed geomagnetic field lines. Observations of events associated with co-rotating regions of enhanced proton flux in interplanetary space were used to establish the characteristics of the 1.2 to 40 MeV proton access windows. The results were compared to particle access predictions of the distant geomagnetic tail configurations. The role played by interplanetary anisotropies in the observation of persistent polar cap features is discussed. Special emphasis is given to the problem of nonadiabatic particle entry through regions where the magnetic field is changing direction.

  10. 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.

  11. Magnetic Patches in Internetwork Quiet Sun

    NASA Astrophysics Data System (ADS)

    De Wijn, Alfred; Lites, B.; Berger, T.; Shine, R.; Title, A.; Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Hinode Team

    2007-05-01

    We study strong flux elements in the quiet sun in the context of the nature of quiet-sun magnetism, its coupling to chromospheric, transition-region and coronal fields, and the nature of a local turbulent dynamo. Strong, kilogauss flux elements show up intermittently as small bright points in G-band and Ca II H images. Although bright points have been extensively studied in the magnetic network, internetwork magnetism has only come under scrutiny in recent years. A full spectrum of field strengths seems to be ubiquitously present in the internetwork at small spatial scales, with the stronger elements residing in intergranular lanes. De Wijn et al. (2005) found that bright points in quiet sun internetwork areas appear recurrently with varying intensity and horizontal motion within long-lived patches that outline cell patterns on mesogranular scales. They estimate that the "magnetic patches" have a mean lifetime of nine hours, much longer than granular timescales. We use multi-hour sequences of G-band and Ca II H images as well as magnetograms recorded by the Hinode satellite to follow up on their results. The larger field of view, the longer sequences, the addition of magnetograms, and the absence of atmospheric seeing allows us to better constrain the patch lifetime, to provide much improved statistics on IBP lifetime, to compare IBPs to network bright points, and to study field polarity of IBPs in patches and between nearby patches. Hinode is an international project supported by JAXA, NASA, PPARC and ESA. We are grateful to the Hinode team for all their efforts in the design, build and operation of the mission.

  12. Design of Quiet Rotorcraft Approach Trajectories

    NASA Technical Reports Server (NTRS)

    Padula, Sharon L.; Burley, Casey L.; Boyd, D. Douglas, Jr.; Marcolini, Michael A.

    2009-01-01

    A optimization procedure for identifying quiet rotorcraft approach trajectories is proposed and demonstrated. The procedure employs a multi-objective genetic algorithm in order to reduce noise and create approach paths that will be acceptable to pilots and passengers. The concept is demonstrated by application to two different helicopters. The optimized paths are compared with one another and to a standard 6-deg approach path. The two demonstration cases validate the optimization procedure but highlight the need for improved noise prediction techniques and for additional rotorcraft acoustic data sets.

  13. The quiet revolution of numerical weather prediction

    NASA Astrophysics Data System (ADS)

    Bauer, Peter; Thorpe, Alan; Brunet, Gilbert

    2015-09-01

    Advances in numerical weather prediction represent a quiet revolution because they have resulted from a steady accumulation of scientific knowledge and technological advances over many years that, with only a few exceptions, have not been associated with the aura of fundamental physics breakthroughs. Nonetheless, the impact of numerical weather prediction is among the greatest of any area of physical science. As a computational problem, global weather prediction is comparable to the simulation of the human brain and of the evolution of the early Universe, and it is performed every day at major operational centres across the world.

  14. The quiet revolution of numerical weather prediction.

    PubMed

    Bauer, Peter; Thorpe, Alan; Brunet, Gilbert

    2015-09-03

    Advances in numerical weather prediction represent a quiet revolution because they have resulted from a steady accumulation of scientific knowledge and technological advances over many years that, with only a few exceptions, have not been associated with the aura of fundamental physics breakthroughs. Nonetheless, the impact of numerical weather prediction is among the greatest of any area of physical science. As a computational problem, global weather prediction is comparable to the simulation of the human brain and of the evolution of the early Universe, and it is performed every day at major operational centres across the world.

  15. Delayed stochastic differential model for quiet standing

    NASA Astrophysics Data System (ADS)

    Yao, W.; Yu, P.; Essex, C.

    2001-02-01

    A physiological quiet standing model, described by a delayed differential equation, subject to a white noise perturbation, is proposed to study the postural control system of human beings. It has been found that the white noise destabilizes the equilibrium state, and inertia accelerates the destabilizing process, and that the position of a person is detected and processed by the person's nervous system with a delay. This paper focuses on the analysis of Hopf bifurcation and its stability in this context. Based on the analytical predictions confirmed by numerical simulations, it has been shown that the posture of a person is controlled in such a way that possible amplitude oscillations are minimized.

  16. Initial geomagnetic field model from Magsat vector data

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    Magsat data from the magnetically quiet days of November 5-6, 1979, were used to derive a thirteenth degree and order spherical harmonic geomagnetic field model, MGST(6/80). The model utilized both scalar and high-accuracy vector data and fit that data with root-mean-square deviations of 8.2, 6.9, 7.6 and 7.4 nT for the scalar magnitude, B(r), B(theta), and B(phi), respectively. The model includes the three first-order coefficients of the external field. Comparison with averaged Dst indicates that zero Dst corresponds with 25 nT of horizontal field from external sources. When compared with earlier models, the earth's dipole moment continues to decrease at a rate of about 26 nT/yr. 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 WC80, AWC/75 and IGS/75 are better for predicting vector fields.

  17. 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.

  18. 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.

  19. Meta-analyzed heart rate variability, exposure to geomagnetic storms, and the risk of ischemic heart disease.

    PubMed

    Baevsky, R M; Petrov, V M; Cornelissen, G; Halberg, F; Orth-Gomer, K; Akerstedt, T; Otsuka, K; Breus, T; Siegelova, J; Dusek, J; Fiser, B

    1997-07-01

    The aim was to examine how heart rate variability (HRV) relates to the risk of ischemic heart disease (IHD) and may provide a means to assess effects of exposure to geomagnetic storms. In Stockholm, the 24-hour SD of hourly estimates of heart rate (HR) were obtained by Holter monitoring from 50 men who had had an acute myocardial infarction or had angina pectoris and compared to that of 50 clinically healthy men of similar age. In Tokyo, the HR 121 normotensives and 176 treated hypertensives was monitored. The incidence of IHD was recorded prospectively for 6 years. These results are aligned with those of a retrospective analysis of archived data on all crews of the Soyuz spacecraft for 1990-1994 focused on ECG from cosmonauts (47 male and 2 female) at times corresponding to geomagnetic storms. The results clearly indicate a decrease in HRV in association with IHD (20.5%, p=0.002 in Stockholm, 20.0%, p=0.04 in Tokyo). By comparison, the about 30% decrease (p=0.041) in rms SD of HR in cosmonauts studied during a geomagnetic storm as compared to cosmonauts monitored on quiet days adds supportive evidence to the proposition that exposure to geomagnetic disturbances increases cardiovascular disease risk.

  20. The Temperature and Density Structure of the Quiet Solar Corona

    NASA Astrophysics Data System (ADS)

    Winebarger, A. R.; Warren, H. P.

    2001-05-01

    The temperature and density structure of the quiet solar corona remains unclear. In this poster, we will present a preliminary analysis of a quiet solar coronal loop structure observed with SOHO and TRACE. After determining the magnetic field structure from potential field extrapolation, we attempt to model this loop using RTV scaling laws with various heating functions. This work is in preparation for a full-scale statistical study of SOHO/TRACE data to determine the structure of the quiet solar corona.

  1. Towards High Reynolds Number Quiet Flow in Hypersonic Tunnels

    DTIC Science & Technology

    2009-02-23

    design methodology was developed to determine the optimal shape of the supersonic nozzle to achieve laminar flow on the nozzle walls and hence quiet...fully automated optimal design methodology was developed to determine the optimal shape of the supersonic nozzle to achieve laminar flow on the... nozzle walls and maximize the length of the region of quiet flow in the test section. In the latter case, detailed time-accurate numerical simulations

  2. 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.

  3. Decreased Stress Levels in Nurses: A Benefit of Quiet Time.

    PubMed

    Riemer, Heather C; Mates, Joanna; Ryan, Linda; Schleder, Bonnie J

    2015-09-01

    The benefits of quiet time, a therapeutic method of improving the health care environment, have been evaluated in patients, but only a few studies have examined the effects of quiet time on intensive care nurses. To evaluate the effects of implementing quiet time in a medical-surgical intensive care unit on levels of light, noise, and nurses' stress. Quiet time consisted of turning down the unit lights for a designated time. Levels of light, noise, and nurses' stress were measured. Nurses' stress levels were measured by using a 100-point visual analog scale; unit noise, by using a digital sound level meter (model 407736, Extech Instruments); and unit light, by using an illumination light meter (model 615, Huygen Corporation). Measurements were obtained 30 minutes before and 30 minutes, 1 hour, and 2 hours after implementation of quiet time. Analysis of variance and comparisons of means indicated that both light levels and nurses' stress levels were significantly decreased after quiet time (both P < .001). Noise levels were also decreased after quiet time, but the decrease was not significant (P = .08). Use of quiet time resulted in decreased light levels and decreased stress levels among nurses. Quiet time is an easily performed energy-saving intervention to promote a healthy work environment. ©2015 American Association of Critical-Care Nurses.

  4. Sharks can detect changes in the geomagnetic field

    PubMed Central

    Meyer, Carl G; Holland, Kim N; Papastamatiou, Yannis P

    2004-01-01

    We used behavioural conditioning to demonstrate that sharks can detect changes in the geomagnetic field. Captive sharks were conditioned by pairing activation of an artificial magnetic field with presentation of food over a target. Conditioned sharks subsequently converged on the target when the artificial magnetic field was activated but no food reward was presented thereby demonstrating that they were able to sense the altered magnetic field. This strong response provides a robust behavioural assay that could be used to determine how sharks detect magnetic fields and to measure detection thresholds. PMID:16849172

  5. Joint coordination during quiet stance: effects of vision.

    PubMed

    Krishnamoorthy, Vijaya; Yang, Jeng-Feng; Scholz, John P

    2005-07-01

    Stabilization of the center of mass (CM) is an important goal of the postural control system. Coordination of several joints along the human "pendulum" is required to achieve this goal. We studied the coordination among body segments with respect to horizontal CM stabilization during a quiet stance task and the effects of vision on CM stability. Subjects were asked to stand quietly on a narrow wooden block supporting only the mid-foot, with either open (EO) or closed (EC) eyes on separate trials. Instant equilibrium points (IEPs) in the center of pressure (CP) trajectory were determined when the horizontal component of the ground reaction force was zero and the CP data were decomposed into their rambling and trembling components. The joint angle, CM and CP data were divided into short cycles (time-normalized to 100 data points) or longer segments (time-normalized to 1000 data points) of equal length beginning and ending in an IEP. Motor abundance with respect to patterns of joint coordination was evaluated using the uncontrolled manifold (UCM) approach. Here, a UCM is a subspace spanning all joint combinations resulting in a given CM position. All combinations of joint angles that lie within this subspace are equivalent with respect to that CM position while joint angle combinations lying in a subspace orthogonal to the UCM lead to deviation from that CM position. UCM analysis was performed on data organized either across time within longer segments or at each point in time across multiple segments or across multiple cycles. Regardless of method of analysis, most of the variance in joint space was constrained to be within the UCM, preserving the mean CM position in both the EO and EC conditions. Joint configuration variance was significantly higher in the EC than in the EO condition although this increase occurred primarily within the UCM rather than in the orthogonal subspace that would have led to variation of the CM position. These results demonstrate the

  6. 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.

  7. Brief quiet ego contemplation reduces oxidative stress and mind-wandering

    PubMed Central

    Wayment, Heidi A.; Collier, Ann F.; Birkett, Melissa; Traustadóttir, Tinna; Till, Robert E.

    2015-01-01

    Excessive self-concern increases perceptions of threat and defensiveness. In contrast, fostering a more inclusive and expanded sense of self can reduce stress and improve well-being. We developed and tested a novel brief intervention designed to strengthen a student’s compassionate self-identity, an identity that values balance and growth by reminding them of four quiet ego characteristics: detached awareness, inclusive identity, perspective taking, and growth. Students (N = 32) in their first semester of college who reported greater self-protective (e.g., defensive) goals in the first 2 weeks of the semester were invited to participate in the study. Volunteers were randomly assigned to one of three conditions: quiet ego contemplation (QEC), QEC with virtual reality (VR) headset (QEC-VR), and control. Participants came to the lab three times to engage in a 15-min exercise in a 30-days period. The 15-min QEC briefly described each quiet ego characteristic followed by a few minutes time to reflect on what that characteristic meant to them. Those in the QEC condition reported improved quiet ego characteristics and pluralistic thinking, decreases in a urinary marker of oxidative stress, and reduced mind-wandering on a cognitive task. Contrary to expectation, participants who wore the VR headsets while listening to the QEC demonstrated the least improvement. Results suggest that a brief intervention that reduces self-focus and strengthens a more compassionate self-view may offer an additional resource that individuals can use in their everyday lives. PMID:26483734

  8. Brief quiet ego contemplation reduces oxidative stress and mind-wandering.

    PubMed

    Wayment, Heidi A; Collier, Ann F; Birkett, Melissa; Traustadóttir, Tinna; Till, Robert E

    2015-01-01

    Excessive self-concern increases perceptions of threat and defensiveness. In contrast, fostering a more inclusive and expanded sense of self can reduce stress and improve well-being. We developed and tested a novel brief intervention designed to strengthen a student's compassionate self-identity, an identity that values balance and growth by reminding them of four quiet ego characteristics: detached awareness, inclusive identity, perspective taking, and growth. Students (N = 32) in their first semester of college who reported greater self-protective (e.g., defensive) goals in the first 2 weeks of the semester were invited to participate in the study. Volunteers were randomly assigned to one of three conditions: quiet ego contemplation (QEC), QEC with virtual reality (VR) headset (QEC-VR), and control. Participants came to the lab three times to engage in a 15-min exercise in a 30-days period. The 15-min QEC briefly described each quiet ego characteristic followed by a few minutes time to reflect on what that characteristic meant to them. Those in the QEC condition reported improved quiet ego characteristics and pluralistic thinking, decreases in a urinary marker of oxidative stress, and reduced mind-wandering on a cognitive task. Contrary to expectation, participants who wore the VR headsets while listening to the QEC demonstrated the least improvement. Results suggest that a brief intervention that reduces self-focus and strengthens a more compassionate self-view may offer an additional resource that individuals can use in their everyday lives.

  9. Comparison of GPS-TEC variation during quiet and disturbed period using the Holt-Winter method and IRI-2012 model over Malaysia

    NASA Astrophysics Data System (ADS)

    Ahmed Ismail, Nouf Abd Emunim; Abdullah, Mardina; Hasbi, Alina Marie

    2016-07-01

    Total Electron Content (TEC) is the main parameter in the ionosphere that has significant effects on radio wave; it changes the speed and direction of the signal propagation, causing the delay of the Global Positioning System (GPS) signals. Therefore, it is crucial to validate the performance of the ionospheric model to reveal the variety of ionospheric behaviour during quiet and disturbed period. This research presents the performance evaluation of the statistical Holt-Winter method and IRI-2012 model using three topside electron density options: IRI-2001, IRI01-corr and NeQuick with the observed GPS-TEC during quiet and disturbed period. The GPS-TEC data were derived from the dual frequency GPS receiver at JUPEM (Department of Survey and Mapping Malaysia), from the UUMK station (north Peninsular Malaysia) at geographic coordinates of 6.46°N-100.50°E and geomagnetic coordinates of 3.32°S-172.99°E and TGPG station (south Peninsular Malaysia) at geographic coordinates of 1.36°N-104.10°E and geomagnetic coordinates of 8.43°S -176.53°E, during March of 2013. The maximum value of the GPS-TEC was at the post noon time at 17:00 LT and the minimum was in the early morning from 6:00-7:00 LT. During the quiet period, the maximum GPS-TEC at the UUMK station was 52 TECU while at the TGPG station, it was 60 TECU. During the disturbed period, when intense geomagnetic storm occurred on 17 March 2013, the maximum GPS-TEC recorded was 58 TECU and 65 TECU in UUMK and TGPG station, respectively. The diurnal hourly variation during the quiet period indicated that IRI-2001, IRI01-corr, and NeQuick had overestimation agreement during the day hours except for the time between 11:00-19:00 LT when IRI01-corr and NeQuick showed underestimation, while during 13:00-20:00 LT, IRI-2001 showed slight underestimation whereas the Holt-Winter method showed good agreement with GPS-TEC. During the disturbed period, IRI-2001 showed overestimation agreement for all hours, while the IRI01-corr

  10. A new regard about Surlari National Geomagnetic Observatory

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    Geomagnetic field study in Romanian stations has started with irregular measurements in late XIXth century. In 1943, the foundation of Surlari National Geomagnetic Observatory (SNGO) marks the beginning of a new era in the systematic study of geomagnetic field by a continuous registration of its variations and by carrying out standard absolute measurements in a fundamental station. The location of the observatory meets the highest exigencies, being situated in physical-geological conditions of a uniform local field, at a reasonably long distance from human activities. Its laboratories observe strict conditions of non-magnetism, ensuring the possibility of absolute standard measurements (national magnetic standards) for all the units in the country, civil or military, which are endowed with equipment based on geomagnetic metrology. These basic conditions have allowed the observatory to become by developing its initial preoccupations a centre of complex geomagnetic research, constantly involved in national and international issues, promoting new themes in our country and bringing significant contributions. During the last two decades, infrastructure and equipment used in monitoring geomagnetic field at European and planetary level have experienced a remarkable development. New registering techniques have allowed a complete to automate of data acquisition, and sampling step and their precision increased by two classes of size. Systems of transmitting these data in real time to world collecting centres have resulted in the possibility of approaching globalize studies, suitable for following some phenomena at planetary scale. At the same time, a significant development in the procedures of processing primary data has been registered, based on standardized programmes. The new stage of this fundamental research, largely applicable in various fields, is also marked by the simultaneous observation of space-time distribution of terrestrial electromagnetic field by means of

  11. Geomagnetic Navigation of Autonomous Underwater Vehicle Based on Multi-objective Evolutionary Algorithm.

    PubMed

    Li, Hong; Liu, Mingyong; Zhang, Feihu

    2017-01-01

    This paper presents a multi-objective evolutionary algorithm of bio-inspired geomagnetic navigation for Autonomous Underwater Vehicle (AUV). Inspired by the biological navigation behavior, the solution was proposed without using a priori information, simply by magnetotaxis searching. However, the existence of the geomagnetic anomalies has significant influence on the geomagnetic navigation system, which often disrupts the distribution of the geomagnetic field. An extreme value region may easily appear in abnormal regions, which makes AUV lost in the navigation phase. This paper proposes an improved bio-inspired algorithm with behavior constraints, for sake of making AUV escape from the abnormal region. First, the navigation problem is considered as the optimization problem. Second, the environmental monitoring operator is introduced, to determine whether the algorithm falls into the geomagnetic anomaly region. Then, the behavior constraint operator is employed to get out of the abnormal region. Finally, the termination condition is triggered. Compared to the state-of- the-art, the proposed approach effectively overcomes the disturbance of the geomagnetic abnormal. The simulation result demonstrates the reliability and feasibility of the proposed approach in complex environments.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Airesearch QCGAT program. [quiet clean general aviation turbofan engines

    NASA Technical Reports Server (NTRS)

    Heldenbrand, R. W.; Norgren, W. M.

    1979-01-01

    A model TFE731-1 engine was used as a baseline for the NASA quiet clean general aviation turbofan engine and engine/nacelle program designed to demonstrate the applicability of large turbofan engine technology to small general aviation turbofan engines, and to obtain significant reductions in noise and pollutant emissions while reducing or maintaining fuel consumption levels. All new technology design for rotating parts and all items in the engine and nacelle that contributed to the acoustic and pollution characteristics of the engine system were of flight design, weight, and construction. The major noise, emissions, and performance goals were met. Noise levels estimated for the three FAR Part 36 conditions, are 10 t0 15 ENPdB below FAA requirements; emission values are considerably reduced below that of current technology engines; and the engine performance represents a TSFC improvement of approximately 9 percent over other turbofan engines.

  18. No quiet surrender: molecular guardians in multiple sclerosis brain

    PubMed Central

    Steinman, Lawrence

    2015-01-01

    The brain under immunological attack does not surrender quietly. Investigation of brain lesions in multiple sclerosis (MS) reveals a coordinated molecular response involving various proteins and small molecules ranging from heat shock proteins to small lipids, neurotransmitters, and even gases, which provide protection and foster repair. Reduction of inflammation serves as a necessary prerequisite for effective recovery and regeneration. Remarkably, many lesion-resident molecules activate pathways leading to both suppression of inflammation and promotion of repair mechanisms. These guardian molecules and their corresponding physiologic pathways could potentially be exploited to silence inflammation and repair the injured and degenerating brain and spinal cord in both relapsing-remitting and progressive forms of MS and may be beneficial in other neurologic and psychiatric conditions. PMID:25831441

  19. Microwave properties of a quiet sea

    NASA Technical Reports Server (NTRS)

    Stacey, J.

    1985-01-01

    The microwave flux responses of a quiet sea are observed at five microwave frequencies and with both horizontal and vertical polarizations at each frequency--a simultaneous 10 channel receiving system. The measurements are taken from Earth orbit with an articulating antenna. The 10 channel responses are taken simultaneously since they share a common articulating collector with a multifrequency feed. The plotted flux responses show: (1) the effects of the relative, on-axis-gain of the collecting aperture for each frequency; (2) the effects of polarization rotation in the output responses of the receive when the collecting aperture mechanically rotates about a feed that is fixed; (3) the difference between the flux magnitudes for the horizontal and vertical channels, at each of the five frequencies, and for each pointing position, over a 44 degree scan angle; and (4) the RMS value of the clutter--as reckoned over the interval of a full swath for each of the 10 channels. The clutter is derived from the standard error of estimate of the plotted swath response for each channel. The expected value of the background temperature is computed for each of the three quiet seas. The background temperature includes contributions from the cosmic background, the downwelling path, the sea surface, and the upwelling path.

  20. Observations of Quiet Sun Chromosphere Dynamics

    NASA Astrophysics Data System (ADS)

    Verdoni, Angelo; Denker, C.; Deng, N.; Tritschler, A.

    2007-05-01

    The quiet Sun shows a multitude of fine structure in both the photosphere and chromosphere. Observations with high spatial and temporal resolution are required to study their dynamics. In June 2006, simultaneous broad-band continuum (600 nm) and narrow-band spectroscopic (Hα and Na 589.0 nm) data were obtained of a quiet Sun region near disk center using the Dunn Solar Telescope and high-order adaptive optics at the National Solar Observatory/Sacramento Peak. The time-series of continuum data was restored using the speckle masking technique to achieve almost diffraction-limited resolution across the entire field-of-view (80" by 80"). The spectroscopic data were taken with a two-dimensional spectrometer, which is currently being upgraded for spectro-polarimetry. The Visible-light Imaging Magnetograph (VIM) is a telecentric two-dimensional Fabry-Perot based spectro-polarimeter, which will become one of the first-light instruments of the future 1.6-meter New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO). This work was supported by NSF under grants ATM 00-86999, ATM 02-36945, IIS ITR 03-24816, and AST MRI 00-79482 and by NASA under grant NAG 5-12782.

  1. Ionosphere over Africa: Results from Geomagnetic Field Measurements During International Heliophysical Year IHY

    NASA Astrophysics Data System (ADS)

    Rabiu, A. B.; Yumoto, K.; Falayi, E. O.; Bello, O. R.; Magdas/Cpmn Group

    2011-12-01

    Space Environment Research Centre of Kyushu University, Japan, installed 13 units of Magnetic Data Acquisition Systems MAGDAS over Africa during the International Heliophysical Year IHY. Magnetic records from 10 stations along the African 96o Magnetic Meridian (Geographical 30° - 40° East) were examined for Solar quiet daily Sq variations in the two geomagnetic field components H and D. Latitudinal variations of Sq in the geomagnetic components were examined. Signatures of equatorial electrojet and worldwide Sq were identified and studied in detail. H field experienced more variation within the equatorial electrojet zone. Diurnal variations of the geomagnetic variations in the two components were discussed. Sq H is expectedly consistently maximum within the electrojet zone as a result of EEJ. Sq D has maximum values at about -20ɛ (sunrise), -10ɛ (noon time) and +10ɛ (sunset). Levels of inter-relationships between the Sq and its variability in the two components were statistically derived and interpreted in line with the mechanisms responsible for the variations of the geomagnetic field. Data from 2 magnetic observatories within equatorial electrojet EEJ strip and 2 stations outside the EEJ strip were employed to evaluate and study the signatures of the Equatorial electrojet over the African sector. The transient variations of the EEJ at two almost parallel axes using Lagos-Ilorin (West Africa) and Nairobi-Addis Ababa (East Africa) pairs were examined. The eastern electrojet appeared stronger than the western. The latitudinal and longitudinal profiles of the Sq were examined and inferences drawn from observed results were discussed.

  2. Oxygen escape from the Earth during geomagnetic reversals: Implications to mass extinction

    NASA Astrophysics Data System (ADS)

    Wei, Yong; Pu, Zuyin; Zong, Qiugang; Wan, Weixing; Ren, Zhipeng; Fraenz, Markus; Dubinin, Eduard; Tian, Feng; Shi, Quanqi; Fu, Suiyan; Hong, Minghua

    2014-05-01

    The evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field intensity. Oxygen can escape into interplanetary space as ions after gaining momentum from solar wind, but Earth's strong dipole field reduces the momentum transfer efficiency and the ion outflow rate, except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes Mars-like in morphology. The newest databases available for the Phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of years. We propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level, which is known to be a cause of mass extinction. We simulated the oxygen ion escape rate for the Triassic-Jurassic event, using a modified Martian ion escape model with an input of quiet solar wind inferred from Sun-like stars. The results show that geomagnetic reversal could enhance the oxygen escape rate by 3-4 orders only if the magnetic field was extremely weak, even without consideration of space weather effects. This suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass extinction. Therefore, if this causal relation indeed exists, it should be a "many-to-one" scenario rather the previously considered "one-to-one", and planetary magnetic field should be much more important than previously thought for planetary habitability.

  3. The driving mechanisms of particle precipitation during the moderate geomagnetic storm of 7 January 2005

    NASA Astrophysics Data System (ADS)

    Longden, N.; Honary, F.; Kavanagh, A. J.; Manninen, J.

    2007-10-01

    The arrival of an interplanetary coronal mass ejection (ICME) triggered a sudden storm commencement (SSC) at ~09:22 UT on the 7 January 2005. The ICME followed a quiet period in the solar wind and interplanetary magnetic field (IMF). We present global scale observations of energetic electron precipitation during the moderate geomagnetic storm driven by the ICME. Energetic electron precipitation is inferred from increases in cosmic noise absorption (CNA) recorded by stations in the Global Riometer Array (GLORIA). No evidence of CNA was observed during the first four hours of passage of the ICME or following the sudden commencement (SC) of the storm. This is consistent with the findings of Osepian and Kirkwood (2004) that SCs will only trigger precipitation during periods of geomagnetic activity or when the magnetic perturbation in the magnetosphere is substantial. CNA was only observed following enhanced coupling between the IMF and the magnetosphere, resulting from southward oriented IMF. Precipitation was observed due to substorm activity, as a result of the initial injection and particles drifting from the injection region. During the recovery phase of the storm, when substorm activity diminished, precipitation due to density driven increases in the solar wind dynamic pressure (Pdyn) were identified. A number of increases in Pdyn were shown to drive sudden impulses (SIs) in the geomagnetic field. While many of these SIs appear coincident with CNA, SIs without CNA were also observed. During this period, the threshold of geomagnetic activity required for SC driven precipitation was exceeded. This implies that solar wind density driven SIs occurring during storm recovery can drive a different response in particle precipitation to typical SCs.

  4. 49 CFR 222.38 - Can a quiet zone be created in the Chicago Region?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Can a quiet zone be created in the Chicago Region... § 222.38 Can a quiet zone be created in the Chicago Region? Public authorities that are eligible to establish quiet zones under this part may create New Quiet Zones or New Partial Quiet Zones in the Chicago...

  5. Tango in the Mid-Jurassic: 10,000-Yr Geomagnetic Field Reversals

    NASA Astrophysics Data System (ADS)

    Steiner, M.

    2001-12-01

    A continuous magnetostratigraphic signature of Layer 2A from Jurassic Quiet Zone (JQZ) oceanic crust now is known from two separate paleo-magnetic data sets. Measurement/demagnetization along the length of the entire core at 5-cm intervals generated ~100,000 data points, whereas a suite of 472 discrete samples also were taken from throughout the core. Both data sets display the same magnetization pattern, a series of repeated sinusoidal inclination changes downhole. Six inter-vals of maximum inclination (three positive, three negative) are obser-ved. Maximum inclination intervals of +/-40° are separated by regions of smoothly varying intermediate inclination values. Despite lack of azmuithal orientation of the core, downhole magnetic logging (Larson et al., in prep.) shows full ~360° directional change in the magnetization vector. Therefore, the maximum inclination regions represent polarity intervals of the geomagnetic field, and six polarity intervals in stacked sequence are contained in the upper 400 m thickness of Layer 2A at this site. The time duration spanned by these six reversals was estimated from recent seismic studies of young ocean crustal construction on the East Pacific Rise (EPR). Estimates of completion of construction of Layer 2A within 1-3 km from the rise crest and typical EPR half-spreading rates of 5-8 cm/yr suggest that the studied 400 m of ocean crust represents 37,000-60,000 years. The fast construction of EPR crust implies that the Middle Jurassic geomagnetic field was reversing at a phenomenal rate of 5000-10,000 years. These data establish that the `quiet' signature in the oldest portion of the lineated magnetic anomaly patterns in the ocean crust is due to exceedingly rapid reversals of the geomagnetic field, because succes-sive, superposed opposite-polarity magnetic signatures will essentially cancel one another out at the sea surface. The width of the 'quiet' magnetic signature in the western Pacific Ocean implies that the 5000

  6. [ON HUMAN BODY REACTION TO A CHANGED GEOMAGNETIC BACKGROUND].

    PubMed

    Sterlikova, I V

    2015-01-01

    Purpose of the work was to test the concept about existence of a heliobiological relation in the Earth's middle-latitude region for which to analyze, as an example, frequency of circulatory disease exacerbation, mental and behavior disorders, and respiratory diseases (bronchial asthma). The subject and object of the experimental statistic survey have been dwellers of city of Murom (Vladimir region) located in middle-latitude geomagnetic region Φ ≈ 53 degrees. The source material in the investigation was medical data of the Murom ambulance service and geophysical data of the Borok geomagnetic observatory (Yaroslavl region). The survey went on 3 years from February, 1985 till December, 1987 and coincided with the rise of the 11th solar cycle. The largest number of calls to the ambulance service due to acute circulatory condition, mental or behavior disorders, respiratory diseases (bronchial asthma particularly) and their fatal outcome fell on periods of long absence of high-frequency geomagnetic pulsation within the frequency range of human biorhythms.

  7. 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.

  8. Geomagnetic activity effects on the equatorial neutral thermosphere

    SciTech Connect

    Burrage, M.D.; Abreu, V.J.; Orsini, N. ); Fesen, C.G. ); Roble, R.G. )

    1992-04-01

    The effects of geomagnetic activity on the equatorial neutral thermosphere are investigated with mass spectrometer measurements from the Atmosphere Explorer E (AE-E) satellite and simulations generated by the National Center for Atmospheric Research thermosphere/ionosphere general circulation model (TIGCM). A study of the local time dependence of the equatorial geomagnetic storm response concentrates on a disturbed period from March 20 (day 79) to March 31 (day 90), 1979. This interval was the subject of an intense data-gathering and analysis campaign for the Coordinated Data Analysis Workshop 6, and global TIGCM predictions are available for the specific conditions of the storm as a function of universal time. The AE-E measurements demonstrate that significant geomagnetic storm-induced perturbations of upper thermospheric N{sub 2} and O densities extend into the equatorial zone but are mainly restricted to the midnight/early morning sector. The qualitative features of the observations are reproduced by the TIGCM, although in general, the model simulations overestimate the storm temperature and density enhancements, primarily in the nighttime thermosphere. This suggests that either the nighttime cooling rates in the TIGCM are too small or that the specified auroral forcing of the model are too persistent.

  9. Cycle 22; Geomagnetic storm threats to power systems continue

    SciTech Connect

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

    1991-09-01

    This paper reports that for many electric utility systems, Solar Cycle 22 has been the first introduction to the phenomena of Geomagnetic Disturbances and the disrupting and damaging effects that they can have upon modern power systems. For all intents and purposes, Power Industry awareness of Cycle 22 started with a bang during the Great Geomagnetic Storm of March 13, 1989. This storm caused a blackout to the entire Province of Quebec, permanently damaged a large nuclear plant GSU transformer in New Jersey, and created enough havoc across the entire North American power grid to create the plausible threat of a massive power system blackout. The flurry of activity and investigation that followed has led many engineers to realize that their power systems are indeed vulnerable to this phenomena and if anything are becoming ever more vulnerable as the system grows to meet future requirements. As a result some organizations such as Hydro Quebec, PSE and G, and the PJM Pool now implement strategic measures as a remedial response to detection of geomagnetic storm conditions. Many more companies pay particularly close attention to storm forecasts and alerts, and the industry in general has accelerated research and monitoring activities through their own means of in concert with the Electric Power Research Institute (EPRI).

  10. Centennial increase in geomagnetic activity: Latitudinal differences and global estimates

    NASA Astrophysics Data System (ADS)

    Mursula, K.; Martini, D.

    2006-08-01

    We study here the centennial change in geomagnetic activity using the newly proposed Inter-Hour Variability (IHV) index. We correct the earlier estimates of the centennial increase by taking into account the effect of the change of the sampling of the magnetic field from one sample per hour to hourly means in the first years of the previous century. Since the IHV index is a variability index, the larger variability in the case of hourly sampling leads, without due correction, to excessively large values in the beginning of the century and an underestimated centennial increase. We discuss two ways to extract the necessary sampling calibration factors and show that they agree very well with each other. The effect of calibration is especially large at the midlatitude Cheltenham/Fredricksburg (CLH/FRD) station where the centennial increase changes from only 6% to 24% caused by calibration. Sampling calibration also leads to a larger centennial increase of global geomagnetic activity based on the IHV index. The results verify a significant centennial increase in global geomagnetic activity, in a qualitative agreement with the aa index, although a quantitative comparison is not warranted. We also find that the centennial increase has a rather strong and curious latitudinal dependence. It is largest at high latitudes. Quite unexpectedly, it is larger at low latitudes than at midlatitudes. These new findings indicate interesting long-term changes in near-Earth space. We also discuss possible internal and external causes for these observed differences. The centennial change of geomagnetic activity may be partly affected by changes in external conditions, partly by the secular decrease of the Earth's magnetic moment whose effect in near-Earth space may be larger than estimated so far.

  11. 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

  12. 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.

  13. 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/

  14. 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.

  15. 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.

  16. 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.

  17. 49 CFR 222.41 - How does this rule affect Pre-Rule Quiet Zones and Pre-Rule Partial Quiet Zones?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Pre-Rule Partial Quiet Zones? 222.41 Section 222.41 Transportation Other Regulations Relating to... Groups of Crossings-Quiet Zones § 222.41 How does this rule affect Pre-Rule Quiet Zones and Pre-Rule...-Rule Quiet Zone may be established by automatic approval and remain in effect, subject to § 222.51,...

  18. 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.

  19. The "Quiet" Troubles of Low-Income Children

    ERIC Educational Resources Information Center

    Weissbourd, Richard

    2009-01-01

    Most of the troubles poor at-risk children have are not "loud" problems like disruptive behavior or gang involvement. They are "quiet." The range of these problems is vast. Hunger, dehydration, asthma, obesity, and hearing problems can all insidiously trip children up in school. Some quiet problems are psychological--depression, anxiety, the fear…

  20. Mired in the Shadows: Quiet Students in Secondary Schools

    ERIC Educational Resources Information Center

    Thompson, Greg; Bell, James

    2011-01-01

    Quiet students are a feature of the organisation of secondary schools. Using qualitative methods and Deleuzean conceptualisations of modern subjectivity, this paper explores the ways that quiet students negotiate the terrain of their school. These negotiations often seem to produce a self that is trapped rather than a subject who seizes…

  1. Quiet standing after carbohydrate ingestion induces sympathoexcitatory and pressor responses in young healthy males.

    PubMed

    Cao, Lei; Pilowsky, Paul M

    2014-10-01

    To investigate the role of the sympathetic nervous system in the cardiovascular response to quiet standing in the postprandial state. Following a 30min pre-ingestion phase, 14 healthy young male subjects consumed a 600kcal carbohydrate-rich meal. Arterial blood pressure (BP) and heart rate (HR) were recorded for a further 120min. Measurements were obtained (Finometer) in both the supine (5min) and standing (5min) condition every 30min. Power spectral analysis of RR-interval and BP variability was calculated, and heart rate responses to the baroreceptor reflex were calculated to estimate spontaneous baroreflex sensitivity (sBRS). Derived stroke volume (SV) was measured to track changes to postural stress postprandially. Quiet standing increased RR-interval low frequency power, ratio of RR-interval low frequency power/high frequency power (ratio of RR LF/HF), and systolic BP low frequency power (SBP LF power), and decreased RR HF power and sBRS before, and after eating. After meal ingestion, SBP LF power increased and sBRS decreased in lying and standing conditions. During quiet standing postprandially, DBP and the mean arterial pressure increased (P<0.01). The increased BP is associated with increased SV (P<0.05) early postprandially, and increased SBP LF power (P<0.01) in the later postprandial phase. SBP LF power is inversely correlated with SV postprandially (P<0.001, R(2)=0.96). The findings suggest a sympathetic activation mediated by baroreflex resetting. Quiet standing in the postprandial state enhances sympathetic outflow to the vasculature, increasing BP. SV may be a compensatory factor stabilising BP during quiet standing early postprandially. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  2. The numerical simulation of the cutoff boundaries determined by the solar wind and geomagnetic parameters

    NASA Astrophysics Data System (ADS)

    Chu, Wei; Qin, Gang

    2017-04-01

    In this paper numerical method is used to study the cutoff boundaries at the high latitudes. We investigated the variations of the cutoff latitudes for energetic particles at 450 km altitude during three geomagnetic storms. The numerical results show that the cutoff latitudes of energetic particles can spread widely depending on the interplanetary and geomagnetic conditions. Since the cutoff boundary is not a circular, an elliptical model is used to fit the shape of the cutoff boundary. It is found that the main parameters of this model are controlled by the interplanetary parameters such as interplanetary magnetic field (IMF), the solar wind pressure Pdyn, dipole tilt angle Ps, geomagnetic activity indices Dst and AE, IMF clock angle θ, and so on. The relationships between the elliptical parameters and the interplanetary conditions were studied, and also between the elliptical parameters and the geomagnetic conditions. Quantitatively estimating can make by using the parameters Bz, Pdyn, PS, Dst, AE, IMF clock angle θ and so on. We found that the relationship is substantially more complex than suggested by previous statistical studies. This result on the cutoff latitudes can be used for forecasting the variation of the cosmic rays at high latitudes during the geomagnetic storms.

  3. Biological effects related to geomagnetic activity and possible mechanisms.

    PubMed

    Krylov, Viacheslav V

    2017-06-21

    This review presents contemporary data on the biological effects of geomagnetic activity. Correlations between geomagnetic indices and biological parameters and experimental studies that used simulated geomagnetic storms to detect possible responses of organisms to these events in nature are discussed. Possible mechanisms by which geomagnetic activity influences organisms are also considered. Special attention is paid to the idea that geomagnetic activity is perceived by organisms as a disruption of diurnal geomagnetic variation. This variation, in turn, is viewed by way of a secondary zeitgeber for biological circadian rhythms. Additionally, we discuss the utility of cryptochrome as a biological detector of geomagnetic storms. The possible involvement of melatonin and protein coding by the CG8198 gene in the biological effects of geomagnetic activity are discussed. Perspectives for studying mechanisms by which geomagnetic storms affect organisms are suggested. Bioelectromagnetics. 2017;9999:1-14. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  4. Preliminary Results from the QuietSpike Flight Test

    NASA Technical Reports Server (NTRS)

    Haering, Edward A., Jr.; Cliatt, Larry J., II; Howe, Don; Waithe, Kenrick

    2007-01-01

    This viewgraph presentation reviews the QuietSpike flight test results. It shows the previous tests from Nearfield probes. The presentation then reviews the approach to test the QuietSpike, and shows graphics of the positions of the test vehicles. It also shows the components of the Sonic Boom Probing Noseboom. A graph of the Pressure Over- Under-shoot (Shaped Sonic Boom Demonstration (SSBD)Data) is presented. It reviews the Shock Probing Orientations, explaining that the probing plane is always behind the tail of the QuietSpike jet. Graphs of the Shock Position Geometry (SSBD Data) and the QuietSpike signature as of the test on 12/13/06, Near-Field Probing Directly Under the QuietSpike jet, and Near-Field Probing to Side, Near-Field Probing Above and to Side. Several slides review the Computational Fluid Dynamic models, and results compared to the probe tests.

  5. Quiet(er) marine protected areas.

    PubMed

    Williams, Rob; Erbe, Christine; Ashe, Erin; Clark, Christopher W

    2015-11-15

    A core task in endangered species conservation is identifying important habitats and managing human activities to mitigate threats. Many marine organisms, from invertebrates to fish to marine mammals, use acoustic cues to find food, avoid predators, choose mates, and navigate. Ocean noise can affect animal behavior and disrupt trophic linkages. Substantial potential exists for area-based management to reduce exposure of animals to chronic ocean noise. Incorporating noise into spatial planning (e.g., critical habitat designation or marine protected areas) may improve ecological integrity and promote ecological resilience to withstand additional stressors. Previous work identified areas with high ship noise requiring mitigation. This study introduces the concept of "opportunity sites" - important habitats that experience low ship noise. Working with existing patterns in ocean noise and animal distribution will facilitate conservation gains while minimizing societal costs, by identifying opportunities to protect important wildlife habitats that happen to be quiet.

  6. Trunk accelerometry as a measure of balance control during quiet standing.

    PubMed

    Moe-Nilssen, Rolf; Helbostad, Jorunn L

    2002-08-01

    The goal was to investigate whether body sway measured by trunk accelerometry during quiet standing could differentiate between young and elderly healthy subjects, and between conditions with eyes open and closed on firm and compliant surfaces. Raw data demonstrated poor discrimination, but horizontal transformation to eliminate a constant gravity component disclosed consistent mean differences across groups (P < or = 0.0025), and also between conditions (P < or = 0.0005), except for the most marginal difference. When drift associated with very low frequency body sway was adjusted for, a significant difference appeared also here (P = 0.001). This study indicates that trunk accelerometry can discriminate between populations and conditions during quiet standing. Copyright 2002 Elsevier Science B.V.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  8. 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.

  9. 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.

  10. The nighttime F-region climatology during magnetically quiet periods seen from TIMED/GUVI and DMSP

    NASA Astrophysics Data System (ADS)

    Kil, H.; Paxton, L.; Zhang, Y.; Wolven, B.; Morrison, D.

    2004-12-01

    In this study, we investigate the drivers of the nighttime climatology in the low- and middle-latitude ionosphere during quiet periods using the TIMED/GUVI and DMSP data. The observation results show that the seasonal hemispheric asymmetry in plasma density is primary induced by the summer-to-winter wind circulations while the longitudinal variations of the F-region morphology is produced by the contribution of the zonal winds that depends on the magnetic declination. However, the F-region morphology observed at 625 km from TIMED/GUVI does not precisely conform the morphology observed at 840 km from DMSP. We will discuss the differential neutral wind effect on the F-region morphology depending on the magnetic declination, altitude, and the location of the geomagnetic equator relative to the geographic equator.

  11. [Biphasic response of the human nervous system to geomagnetic storms studied by EEG].

    PubMed

    Belov, D P; Getmanenko, O V; Kiselev, B V

    2001-03-01

    In two subjects: a male phlegmatic, 56, and a female melancholic, 22, the EEG was recorded at resting. The EEG patterns were juxtaposed with the geomagnetic activity index Ar and the solar activity index SF, as well as between themselves. The results revealed qualitatively similar biphasic responses: a generalised diminishing of the EEG spatial synchronisation and, on the next day, a generalised augmentation of the phenomenon, as compared with a prolonged quiet period. A general unspecific stress response is supposed to underlie the aforementioned dynamics, whereas a reduced cortical tone during a magnetic storm and an enhanced one after its cessation correspond to the two phases observed. Specifics of responses in both subjects corresponded to their individual profiles of interhemisphere asymmetry.

  12. Solar Wind Disturbances Related to Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Tan, A.; Lyatsky, W. B.

    2001-12-01

    We used the superposed epoch method to reconstruct a typical behavior of solar wind parameters before and during strong isolated geomagnetic storms. For this analysis we used 130 such geomagnetic storms during the period of 1966-2000. The results obtained show that a typical disturbance in the solar wind responsible for geomagnetic storm generation is associated with the propagation of high-speed plasma flow compressing ambient solar wind plasma and interplanetary magnetic field (IMF) ahead of this high-speed flow. This gives rise to enhanced magnetic field, plasma density, plasma turbulence and temperature, which start to increase several hours before geomagnetic storm onset. However, the IMF Bz (responsible for geomagnetic storm onset) starts to increase significantly later (approximately 6-7 hours after maximal variations in plasma density and IMF By). The time delay between peaks in IMF Bz and plasma density (and IMF By) may be a result of draping of high-speed plasma streams with ambient magnetic field in the (z-y) plane as discussed by some authors. This leads to an increase first in plasma density and IMF By ahead of a high-speed flow, which is followed by an increase in IMF Bz. This simple model allows us to predict that the probability for geomagnetic storm generation should depend on which edge of a high-speed flow encounters the Earth's magnetosphere. The probability for geomagnetic storm generation is expected to be maximal when the flow encounters the magnetosphere by its north-west edge for negative IMF By and south-west edge for positive IMF By.

  13. Impact of the lower atmosphere on the ionosphere response to a geomagnetic superstorm

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.

    2016-09-01

    Numerical simulations in the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM) are performed to elucidate the impacts of lower atmosphere forcing on the ionosphere response to a geomagnetic superstorm. In particular, how the ionosphere variability due to the October 2003 Halloween storm would be different if it occurred in January coincident with a major sudden stratosphere warming (SSW) event is investigated. The TIE-GCM simulations reveal that the E× B vertical drift velocity and total electron content (TEC) respond differently to the geomagnetic forcing when the lower atmosphere forcing is representative of SSW conditions compared to climatological lower atmosphere forcing conditions. Notably, the storm time variations in the E× B vertical drift velocity differ when the SSW-induced zonal mean and tidal variability in the lower thermosphere are considered, and this is in part due to effects of the SSW on the equatorial ionosphere being potentially misinterpreted as being of geomagnetic origin. Differences in the TEC response to the geomagnetic storm can be up to 100% (˜30 TEC unit (TECU: 1 TECU = 1016 el m-2)) of the storm-induced TEC change, and the temporal variability of the TEC during the storm recovery phase is considerably different if SSW effects are considered. The results demonstrate that even during periods of extreme geomagnetic forcing, it is important to consider the effects of lower atmosphere forcing on the ionosphere variability.

  14. Impact of the Lower Atmosphere on the Ionosphere Response to a Geomagnetic Superstorm

    NASA Astrophysics Data System (ADS)

    Pedatella, N. M.

    2016-12-01

    Numerical simulations in the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) are performed to elucidate the impacts of lower atmosphere forcing on the ionosphere response to a geomagnetic superstorm. In particular, how the ionosphere variability due to the October 2003 Halloween storm would be different if it occurred in January coincident with a major sudden stratosphere warming (SSW) event is investigated. The TIE-GCM simulations reveal that the E x B vertical drift velocity and total electron content (TEC) respond differently to the geomagnetic disturbance when the lower atmosphere forcing is representative of SSW conditions compared to climatological lower atmosphere forcing conditions. Notably, the storm time variations in the E x B vertical drift velocity differ when the effects of the SSW are considered, and this is in part due to effects of the SSW on the equatorial ionosphere being potentially misinterpreted as being of geomagnetic origin. Differences in the TEC response to the geomagnetic storm can be up to 100% ( 30 TECU) of the storm induced TEC change, and the temporal variability of the TEC during the storm recovery phase is considerably different if SSW effects are considered. The results demonstrate that even during periods of extreme geomagnetic forcing it is important to consider the effects of lower atmosphere forcing on the ionosphere variability.

  15. Reduced efficiency of magnetotaxis in magnetotactic coccoid bacteria in higher than geomagnetic fields.

    PubMed

    Pan, Yongxin; Lin, Wei; Li, Jinhua; Wu, Wenfang; Tian, Lanxiang; Deng, Chenglong; Liu, Qingsong; Zhu, Rixiang; Winklhofer, Michael; Petersen, Nikolai

    2009-08-19

    Magnetotactic bacteria are microorganisms that orient and migrate along magnetic field lines. The classical model of polar magnetotaxis predicts that the field-parallel migration velocity of magnetotactic bacteria increases monotonically with the strength of an applied magnetic field. We here test this model experimentally on magnetotactic coccoid bacteria that swim along helical trajectories. It turns out that the contribution of the field-parallel migration velocity decreases with increasing field strength from 0.1 to 1.5 mT. This unexpected observation can be explained and reproduced in a mathematical model under the assumption that the magnetosome chain is inclined with respect to the flagellar propulsion axis. The magnetic disadvantage, however, becomes apparent only in stronger than geomagnetic fields, which suggests that magnetotaxis is optimized under geomagnetic field conditions. It is therefore not beneficial for these bacteria to increase their intracellular magnetic dipole moment beyond the value needed to overcome Brownian motion in geomagnetic field conditions.

  16. 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

  17. Behavior of the ionosphere over Europe during two geomagnetic storms which caused tongues of ionization over North America.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Bouza, Marta; Herraiz, Miguel; Rodriguez-Caderot, Gracia; Radicella, Sandro M.

    2015-04-01

    This work presents the effect of two geomagnetic storms on the ionospheric total electron content (TEC) over Europe. Those geomagnetic storms occurred on July 14th, 2013 and February 19th, 2014 and originated a tongue of ionization over North America. Following the criteria of Gonzalez et al.(1994), the July storm can be classified as a moderate one because the Dst index reached a value of -72nT, whereas the February storm as an intense event considering that Dst index dropped to -112nT. For this study we have used RINEX files obtained from GNSS stations belonging to International GPS Service, IGS, EUREF Permanent Network, and University Navstar Consortium, UNAVCO, networks. The data has been divided into two groups in function of the region: Europe or North America. For each group we have used all the available stations. The RINEX files have been processed using a technique developed by Ciraolo (2012) which assumes the ionospheric thin shell model to obtain the vertical total electron content (vTEC) from the slant total electron content (sTEC) at the Ionospheric Pierce Point, IPP, the point where the line-of-sight between the satellite and the ground receiver intersects the ionosphere. The data were obtained at 1 minute sampling in periods of geomagnetic storms and quiet days close to them. In both storms a tongue of ionization, ToI, appeared over North America from afternoon to dusk (between 19:00 and 3:00 GMT). The behavior of the ionosphere over Europe was very different in eachcase. In July, the TEC decreased respect the quiet days during the ToI time. In the February storm the behavior of the ionosphere over Europe was similar to that of a quiet day but the following day appeared a phenomenom similar to the ToI. Ciraolo, L. (2012). Ionospheric Total Electron Content (TEC) from Global Positioning System. Personal Communication. González, W.D., Joselyn, J. A., Kamide, Y., Kroehl, H. W., Rostoker, G., Tsurutani, B. T., Vasyliunas, V. M. (1994). What is a

  18. 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).

  19. 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.

  20. 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

  1. Quiet Clean Short-haul Experimental Engine (QCSEE) clean combustor test report

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A component pressure test was conducted on a F101 PFRT combustor to evaluate the emissions levels of this combustor design at selected under the wing and over the wing operating conditions for the quiet clean short haul experimental engine (QCSEE). Emissions reduction techniques were evaluated which included compressor discharge bleed and sector burning in the combustor. The results of this test were utilized to compare the expected QCSEE emissions levels with the emission goals of the QCSEE engine program.

  2. Response of nighttime equatorial and low latitude F-region to the geomagnetic storm of August 18, 2003, in the Brazilian sector

    NASA Astrophysics Data System (ADS)

    Sahai, Y.; Becker-Guedes, F.; Fagundes, P. R.; Lima, W. L. C.; Otsuka, Y.; Huang, C.-S.; Espinoza, E. S.; Pi, X.; de Abreu, A. J.; Bolzan, M. J. A.; Pillat, V. G.; Abalde, J. R.; Pimenta, A. A.; Bittencourt, J. A.

    This paper presents an investigation of geomagnetic storm effects in the equatorial and low latitude F-region in the Brazilian sector during the intense geomagnetic storm on 18 August, 2003 (SSC 14:21 UT on 17/08; ΣKp = 52+; Ap = 108; ∣Dst∣ max = 168 at 1600 UT on 18/08). Simultaneous ionospheric sounding measurements from two stations, viz., Palmas (10.2°S, 48.2°W; dip latitude 5.7°S) and Sao Jose dos Campos (23.2°S, 45.9°W; dip latitude 17.6°S), Brazil, are presented for the nights of 16-17, 17-18 and 18-19 August, 2003 (quiet, disturbed and recovery phases). Both stations are equipped with the Canadian Advanced Digital Ionosonde (CADI). Quiet and disturbed conditions of the F-region ionosphere are compared using data collected from the two stations. The relationship between magnetospheric disturbance and low-latitude ionospheric dynamics, and generation of ionospheric irregularities are discussed. On the disturbed nights (17-18 and 18-19 August), the low latitude station S. J. Campos showed strong enhancements in the F-region critical frequency (foF2), whereas the near equatorial station Palmas showed strong uplifting of the F-layer about 1 h earlier. Normally during the June solstice months (May-August) in the Brazilian sector, large-scale ionospheric irregularities in form of plasma bubbles are rarely observed. On the night of 17-18 August, ionsospheric sounding observations at Palmas showed the presence of bottomside spread-F, whereas on the night of 18-19 August, the observations at Palmas and S. J. Campos showed the presence of plasma bubbles when the storm recovery phase had just started. The complementary GPS data available from several stations in the "Rede Brasileira de Monitoramento Continuo de GPS (Brazilian Network for Continuous GPS Monitoring)" are used to obtain the vertical total electron content (VTEC) and the rate of change of TEC per minute on UT days 18 and 19 August, 2003 and presented. Also, several global ionospheric TEC maps

  3. 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.

  4. The Origin of the Jurassic Quiet Zone -new insights from Hawaiian Jurassic magnetic anomalies (Invited)

    NASA Astrophysics Data System (ADS)

    Tominaga, M.; Tivey, M.; Sager, W. W.

    2013-12-01

    Marine magnetic anomalies recorded in oceanic crust, have played a central role in documenting Earth's magnetic field history as compiled in the geomagnetic polarity timescale (GPTS). The oldest part of the marine record is the Jurassic Quiet Zone (JQZ) (pre-M29 chrons) which is known to be a period when field intensity was low, while reversal rate was high. The origin and character of the JQZ has been the subject of marine magnetic studies over past 20 years in the western Pacific where the oldest and arguably best preserved Jurassic magnetic anomalies create three Jurassic lineation sets (Japanese, Hawaiian, and Phoenix). The Japanese JQZ sequence was extensively investigated by an aeromagnetic and 2 deeptow magnetometer surveys, revealing (i) the presence of lineated anomalies older than M29; (ii) a GPTS record extending from M29 to M44 with a tie to ODP Hole 801C and (iii) remarkably fast reversals that decrease in intensity back in time until M38. Prior to M38 there is a low amplitude zone (LAZ) in anomalies lasting until M42, when both anomaly amplitude and a lineated character reappears around Hole 801C. Recently collected (2011) high quality seasurface marine magnetic anomaly data from the Hawaiian lineations show changes in magnetic anomaly shape and amplitude that are similar in to the Japanese lineations, suggesting that the anomalies record globally coherent geomagnetic field behavior for the Jurassic. Specifically, the strong similarity of anomaly patterns between the Japanese and Hawaiian sequences from M19 to M38 supports the remarkably dynamic geomagnetic field behavior of fast reversals and changing intensity, confirming a proposed record of the GPTS sequence for M29 to M38. While the LAZ in the Hawaiian sequence is not as clear as in the Japanese lineations, we believe we can correlate the earlier M42-M44 sequence between the two sets of lineations. The slower spreading rate in the Hawaiian lineations may contribute to this lack of resolution of

  5. Determination of the Croatian geomagnetic observatory location

    NASA Astrophysics Data System (ADS)

    Verbanac, Giuliana; Vujić, Eugen

    2012-04-01

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

  6. Scaling laws from geomagnetic time series

    USGS Publications Warehouse

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

    1998-01-01

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

  7. 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.

  8. 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.

  9. Coronal mass ejections and large geomagnetic storms

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Bame, S. J.; Mccomas, D. J.; Phillips, J. L.

    1990-01-01

    Previous work indicates that coronal mass ejection (CME) events in the solar wind at 1 AU can be identified by the presence of a flux of counterstreaming solar wind halo electrons (above about 80 eV). Using this technique to identify CMEs in 1 AU plasma data, it is found that most large geomagnetic storms during the interval surrounding the last solar maximum (August 1978 - October 1982) were associated with earth-passage of interplanetary disturbances in which the earth encountered both a shock and the CME driving the shock. However, only about one CME in six encountered by earth was effective in causing a large geomagnetic storm. Slow CMEs which did not interact strongly with the ambient solar wind ahead were particularly ineffective in a geomagnetic sense.

  10. 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

  11. Hemodynamic response characteristics of healthy people to changes in meteorological and geomagnetic factors in the north

    NASA Astrophysics Data System (ADS)

    Zenchenko, T. A.; Varlamova, N. G.

    2015-12-01

    This paper analyzes the influence of variations in meteorological and geomagnetic factors on hemodynamic parameters (HP) in 27 healthy volunteers who are residents of Syktyvkar (daily monitoring of blood pressure (BP) and heart rate (HR) and stroke and cardiac output for the period from December 1, 2003, to December 31, 2004). It is shown that temperature variations and geomagnetic activity level (GMA) make the greatest impact on HP changes (85 and 48% cases, respectively). The BP level increases with decreasing temperature and with increasing levels of GMA. The sensitivity of systolic and diastolic blood pressure to the meteorological and geomagnetic factors is approximately twice as high as the sensitivity of other HP to them. The individual values of seasonal changes in BP parameters are 4-9 mmHg for systolic blood pressure and 3-6 mmHg for diastolic blood pressure. The estimates of the characteristics of meteorological and geomagnetic sensitivity in residents of northern latitudes are in good agreement with the results obtained by us earlier for other climatic zones and geomagnetic conditions, logically complementing and enhancing the common space-time picture of the reactions of the human body to external impacts.

  12. Removal of the local geomagnetic field affects reproductive growth in Arabidopsis.

    PubMed

    Xu, Chunxiao; Wei, Shufeng; Lu, Yan; Zhang, Yuxia; Chen, Chuanfang; Song, Tao

    2013-09-01

    The influence of the geomagnetic field-removed environment on Arabidopsis growth was investigated by cultivation of the plants in a near-null magnetic field and local geomagnetic field (45 µT) for the whole growth period under laboratory conditions. The biomass accumulation of plants in the near-null magnetic field was significantly suppressed at the time when plants were switching from vegetative growth to reproductive growth compared with that of plants grown in the local geomagnetic field, which was caused by a delay in the flowering of plants in the near-null magnetic field. At the early or later growth stage, no significant difference was shown in the biomass accumulation between the plants in the near-null magnetic field and local geomagnetic field. The average number of siliques and the production of seeds per plant in the near-null magnetic field was significantly lower by about 22% and 19%, respectively, than those of control plants. These resulted in a significant reduction of about 20% in the harvest index of plants in the near-null magnetic field compared with that of the controls. These results suggest that the removal of the local geomagnetic field negatively affects the reproductive growth of Arabidopsis, which thus affects the yield and harvest index.

  13. Influence of water vapour on the height distribution of positive ions, effective recombination coefficient and ionisation balance in the quiet lower ionosphere

    NASA Astrophysics Data System (ADS)

    Barabash, V.; Osepian, A.; Dalin, P.

    2014-03-01

    Mesospheric water vapour concentration effects on the ion composition and electron density in the lower ionosphere under quiet geophysical conditions were examined. Water vapour is an important compound in the mesosphere and the lower thermosphere that affects ion composition due to hydrogen radical production and consequently modifies the electron number density. Recent lower-ionosphere investigations have primarily concentrated on the geomagnetic disturbance periods. Meanwhile, studies on the electron density under quiet conditions are quite rare. The goal of this study is to contribute to a better understanding of the ionospheric parameter responses to water vapour variability in the quiet lower ionosphere. By applying a numerical D region ion chemistry model, we evaluated efficiencies for the channels forming hydrated cluster ions from the NO+ and O2+ primary ions (i.e. NO+.H2O and O2+.H2O, respectively), and the channel forming H+(H2O)n proton hydrates from water clusters at different altitudes using profiles with low and high water vapour concentrations. Profiles for positive ions, effective recombination coefficients and electrons were modelled for three particular cases using electron density measurements obtained during rocket campaigns. It was found that the water vapour concentration variations in the mesosphere affect the position of both the Cl2+ proton hydrate layer upper border, comprising the NO+(H2O)n and O2+(H2O)n hydrated cluster ions, and the Cl1+ hydrate cluster layer lower border, comprising the H+(H2O)n pure proton hydrates, as well as the numerical cluster densities. The water variations caused large changes in the effective recombination coefficient and electron density between altitudes of 75 and 87 km. However, the effective recombination coefficient, αeff, and electron number density did not respond even to large water vapour concentration variations occurring at other altitudes in the mesosphere. We determined the water vapour

  14. Near IR observations of Quiet Chromosphere

    NASA Astrophysics Data System (ADS)

    Prasad Choudhary, Debi; Deng, N.; Tejamoortula, U.; Penn, M. J.

    2009-05-01

    We have carried out the observations of quiet solar limb during April 29 to May 1, 2008, March 9-13, 2009 using the vertical spectrograph at the focal plane of McMath-Pierce telescope at Kitt Peak National Observatory. The solar limb was mostly featureless during the observations. The New Infrared Array (NAC) at the exit port of the spectrograph has been used to record the limb spectrum at HeI 1083.0 nm, Hydrogen Paschen beta at 1281.8 nm and Brackett gamma 2165.5 nm wavelength regions. The NAC is a 1024 x 1024 InSb Alladin III Detector operating over 1-5 micron range with high density sampling at 0.018 arc second/pixel. The all-reflective optical train minimizes number of surfaces and eliminates ghosts leading to low scatter, ghost-free optics. The close-cycle cryogenic provides a stable cooling environment over six hour period with an accuracy of about 0.01K leading to low dark current. The low read out noise combined with low scattered light and dark current makes NAC an ideal detector for making high quality infrared spectral observations of solar limb. In this presentation, we shall compare the line parameters of these lines around the solar disk. Acknowledgements: This work is supported by NSF under grant ATM 05-48952 and by NASA under grant NNX08AQ32G.

  15. Quiet Clean Short Haul Experimental Engine

    NASA Image and Video Library

    1973-02-21

    Program manager Carl Ciepluch poses with a model of the Quiet Clean Short Haul Experimental Engine (QCSEE) conceived by the National Aeronautics and Space Administration (NASA) Lewis Research Center. The QCSEE engine was designed to power future short-distance transport aircraft without generating significant levels of noise or pollution and without hindering performance. The engines were designed to be utilized on aircraft operating from small airports with short runways. Lewis researchers investigated two powered-lift designs and an array of new technologies to deal with the shorter runways. Lewis contracted General Electric to design the two QCSEE engines—one with over-the-wing power-lift and one with an under-the-wing design. A scale model of the over-the-wing engine was tested in the Full Scale Tunnel at the Langley Research Center in 1975 and 1976. Lewis researchers investigated both versions in a specially-designed test stand, the Engine Noise Test Facility, on the hangar apron. The QCSEE engines met the goals set out by the NASA researchers. The aircraft industry, however, never built the short-distance transport aircraft for which the engines were intended. Different technological elements of the engine, however, were applied to some future General Electric engines.

  16. MAGNETIC LOOPS IN THE QUIET SUN

    SciTech Connect

    Wiegelmann, T.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Borrero, J. M.; Schmidt, W.; Pillet, V. MartInez; Bonet, J. A.; Domingo, V.; Knoelker, M.; Title, A. M.

    2010-11-10

    We investigate the fine structure of magnetic fields in the atmosphere of the quiet Sun. We use photospheric magnetic field measurements from SUNRISE/IMaX with unprecedented spatial resolution to extrapolate the photospheric magnetic field into higher layers of the solar atmosphere with the help of potential and force-free extrapolation techniques. We find that most magnetic loops that reach into the chromosphere or higher have one footpoint in relatively strong magnetic field regions in the photosphere. Ninety-one percent of the magnetic energy in the mid-chromosphere (at a height of 1 Mm) is in field lines, whose stronger footpoint has a strength of more than 300 G, i.e., above the equipartition field strength with convection. The loops reaching into the chromosphere and corona are also found to be asymmetric in the sense that the weaker footpoint has a strength B < 300 G and is located in the internetwork (IN). Such loops are expected to be strongly dynamic and have short lifetimes, as dictated by the properties of the IN fields.

  17. Quiet swimming at low Reynolds number

    NASA Astrophysics Data System (ADS)

    Andersen, Anders; Wadhwa, Navish; Kiørboe, Thomas

    2015-04-01

    The stresslet provides a simple model of the flow created by a small, freely swimming and neutrally buoyant aquatic organism and shows that the far field fluid disturbance created by such an organism in general decays as one over distance squared. Here we discuss a quieter swimming mode that eliminates the stresslet component of the flow and leads to a faster spatial decay of the fluid disturbance described by a force quadrupole that decays as one over distance cubed. Motivated by recent experimental results on fluid disturbances due to small aquatic organisms, we demonstrate that a three-Stokeslet model of a swimming organism which uses breast stroke type kinematics is an example of such a quiet swimmer. We show that the fluid disturbance in both the near field and the far field is significantly reduced by appropriately arranging the propulsion apparatus, and we find that the far field power laws are valid surprisingly close to the organism. Finally, we discuss point force models as a general framework for hypothesis generation and experimental exploration of fluid mediated predator-prey interactions in the planktonic world.

  18. MAGNETIC BRIGHT POINTS IN THE QUIET SUN

    SciTech Connect

    Sanchez Almeida, J.; Bonet, J. A.; Viticchie, B.

    2010-05-20

    We present a visual determination of the number of bright points (BPs) existing in the quiet Sun, which are structures though to trace intense kG magnetic concentrations. The measurement is based on a 0.''1 angular resolution G-band movie obtained with the Swedish Solar Telescope at the solar disk center. We find 0.97 BPs Mm{sup -2}, which is a factor 3 larger than any previous estimate. It corresponds to 1.2 BPs per solar granule. Depending on the details of the segmentation, the BPs cover between 0.9% and 2.2% of the solar surface. Assuming their field strength to be 1.5 kG, the detected BPs contribute to the solar magnetic flux with an unsigned flux density between 13 G and 33 G. If network and inter-network regions are counted separately, they contain 2.2 BPs Mm{sup -2} and 0.85 BPs Mm{sup -2}, respectively.

  19. Ionospheric irregularities over Bahir Dar, Ethiopia during selected geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Kassa, Tsegaye; Damtie, Baylie

    2017-07-01

    We have analyzed the effect of geomagnetic storms on the occurrence of ionospheric irregularities by considering seven case studies in the period of 2013-2014 over Bahir Dar, Ethiopia (11° N , 38° E). We inferred the irregularity indices from GPS phase fluctuation by computing the median of 1-min rate of change of total electron content (fp) along the ray paths from all satellites observed. The Fp -index was calculated as an hourly average fp -index values along the ray paths from all satellites observed during each hour. Our results revealed that the irregularity level was inhibited during post sunset hours of the main phase of the storms we considered. On average, the irregularity index has dropped from 400 (0.4 TECU/min) during quiet time to 50 (0.05 TECU/min) on disturbed time with an amount of 350 (0.35 TECU/min). However, in some of the cases, immediately after the onset of the storm, we observed the enhancement of irregularities. We found that only the observations on 01 June 2013 and 19 February 2014 exhibited a correspondence of the time of occurrence of the minimum of the Dst-index with inhibition of irregularities noted by other researchers. Our observations of the enhancement of irregularities on 17 March 2013 and 19 February 2014 can partly be explained by the orientation of the IMF BZ . Other measurements such as neutral wind, electric field are required to explain the observations on 29 June 2013, 06 July 2013, 09 November 2013 and 27 February 2014.

  20. Principles underlying the organization of movement initiation from quiet stance.

    PubMed

    Brunt, D; Liu, S M; Trimble, M; Bauer, J; Short, M

    1999-10-01

    The purpose of this study was to determine common principles underlying the programming of movement initiation from quiet stance. Subjects were asked to initiate gait, step over a ruler, or to step over a 10 cm high obstacle at a self-paced speed and as fast as possible. The independent variables were initiation condition (gait initiation, stepping over a ruler or obstacle) and initiation speed (self-paced and as fast as possible). The dependent measures for the stance limb only were the latency between postural soleus (S(1)) EMG inhibition and tibialis anterior (TA) EMG onset, the duration of both TA and soleus (S(2)) activity following TA, duration and slope, impulse, and peak forces of the anterior-posterior (Fx) ground reaction force. Selected timing events were also monitored. Analysis of variance was used to determine main and interaction effects. The following results were obtained. (1) The interval from the inhibition of S(1) postural activity to the onset of TA remained invariant between all conditions. (2) The duration of TA increased and S(2) decreased with an increase in speed of initiation. There was no difference in TA and S(2) duration between the initiation conditions. (3) Time to heel-off remained invariant for all conditions. (4) Prior to heel-off all force variables increased with initiation speed but were similar between initiation conditions. After heel-off force variables were different between speeds and conditions being greater for fast speed and stepping over the obstacle. Two conclusions may be drawn from this study. First, the results indicate that gait initiation consists of two, highly coordinated motor programs. Heel-off of the stance limb is the division between these two programs. Second, our findings also suggest that gait initiation and stepping are governed by the same motor programs.

  1. Quantifications of Geomagnetic Storm Impact on TEC and NmF2 during 2013 Mar. event

    NASA Astrophysics Data System (ADS)

    Shim, J. S.; Tsagouri, I.; Goncharenko, L. P.; Mays, M. L.; Taktakishvili, A.; Rastaetter, L.; Kuznetsova, M. M.

    2016-12-01

    We investigate the ionospheric response to 2013 Mar. geomagnetic storm event using GPS TEC, ISR and ionosonde observations in North American sector. In order to quantify variations of TEC and NmF2 (or foF2) due to the storm, we remove the background quiet-time values (e.g., TEC of one day prior to the storm, NmF2 median and average of five quietest days for 30 days prior to the storm). In addition, in order to assess modeling capability of reproducing storm impacts on TEC and NmF2, we compare the observations with various model simulations, which are obtained from empirical, physics-based, and data assimilation models. Further, we investigate how uncertainty in the interplanetary magnetic field (IMF) impacts on TEC and NmF2 during the geomagnetic storm event. For this uncertainty study, we use a physics-based coupled ionosphere-thermosphere model, CTIPe, and solar wind parameters obtained from ensemble of WSA-ENLIL+Cone model simulations. This study has been supported by the Community Coordinated Modeling Center (CCMC) at the Goddard Space Flight Center. Model outputs and observational data used for the study will be permanently posted at the CCMC website (http://ccmc.gsfc.nasa.gov) for the space science communities to use.

  2. Westward equatorial electrojet during daytime hours. [relation to geomagnetic horizontal field depression

    NASA Technical Reports Server (NTRS)

    Rastogi, R. G.

    1974-01-01

    The phenomenon of the depression of the geomagnetic horizontal field during the daytime hours of magnetically quiet days at equatorial stations is described. These events are generally seen around 0700 and 1600 LT, being more frequent during the evening than the morning hours. The evening events are more frequent during periods of low solar activity and in the longitude region of weak equatorial electrojet currents. The latitudinal extent of the phenomenon is limited to the normal equatorial electrojet region, and on some occasions the phenomenon is not seen at both stations, separated by only a few hours in longitude. During such an event, the latitudinal profile of the geomagnetic vertical field across the equator is reversed, the ionospheric drift near the equator is reversed toward the east, the q type of sporadic E layer is completely absent, and the height of the peak ionization in the F2 region is decreased. It is suggested that these effects are caused by a narrow band of current flowing westward in the E region of the ionosphere and within the latitude region of the normal equatorial electrojet, due to the reversal of the east-west electrostatic field at low latitudes.

  3. POGO satellite orbit corrections: an opportunity to improve the quality of the geomagnetic field measurements?

    NASA Astrophysics Data System (ADS)

    Stockmann, Reto; Christiansen, Freddy; Olsen, Nils; Jackson, Andrew

    2015-06-01

    We present an attempt to improve the quality of the geomagnetic field measurements from the Polar Orbiting Geophysical Observatory (POGO) satellite missions in the late 1960s. Inaccurate satellite positions are believed to be a major source of errors for using the magnetic observations for field modelling. To improve the data, we use an iterative approach consisting of two main parts: one is a main field modelling process to obtain the radial field gradient to perturb the orbits and the other is the state-of-the-art GPS orbit modelling software BERNESE to calculate new physical orbits. We report results based on a single-day approach showing a clear increase of the data quality. That single-day approach leads, however, to undesirable orbital jumps at midnight. Furthermore, we report results obtained for a much larger data set comprising almost all of the data from the three missions. With this approach, we eliminate the orbit discontinuities at midnight but only tiny quality improvements could be achieved for geomagnetically quiet data. We believe that improvements to the data are probably still possible, but it would require the original tracking observations to be found.

  4. 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

    central polar cap (greater than approx. 80 magnetic latitude) antisunward wind speed is found to be a strong function of both solar and geomagnetic activity. The polar cap temperatures show variations in both solar and geomagnetic activity, with temperatures near 800 K for low K(sub p) and F(sub 10.7) and greater than about 2000 K for high K(sub p) and F(sub 10.7). The observed temperatures are significantly greater than those predicted by the mass spectrometer/incoherent scatter model for high activity conditions. Theoretical analysis based on the NCAR TIGCM indicates that the antisunward upper thermospheric winds, driven by upstream ion drag, basically 'coast' across the polar cap. The relatively small changes in wind velocity and direction within the polar cap are induced by a combination of forcing terms of commensurate magnitude, including the nonlinear advection term, the Coriolis term, and the pressure gradient force term. The polar cap thennospheric thermal balance is dominated by horizontal advection, and adiabatic and thermal conduction terms.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. First geomagnetic measurements in the Antarctic region

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  12. 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.

  13. Geomagnetic storm fields near a synchronous satellite.

    NASA Technical Reports Server (NTRS)

    Kawasaki, K.; Akasofu, S. I.

    1971-01-01

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

  14. 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.

  15. QUIET: The Q/U Imaging ExperimenT

    NASA Astrophysics Data System (ADS)

    Newburgh, Laura; QUIET Collaboration

    2010-01-01

    The Q/U Imaging Experiment (QUIET) is a ground-based CMB polarization experiment based on correlation polarimertry using high electron mobility transistor (HEMT) amplifiers. QUIET is designed to measure the CMB polarization on angular scales where the spectrum from inflationary gravity waves is predicted to be maximal. QUIET operates at two frequency bands centered at 40 GHz and 90 GHz. The 40 GHz receiver was deployed in 2008 at 5100m altitude in the Atacama Desert, Chile, and has finished data collection, logging over 3500 hours on the sky and covering 1200 square degrees. The 90 GHz receiver was deployed on the same telescope and started taking data in July 2009. I will present an instrument overview and the status of data analysis from the 40 GHz season. QUIET is supported by NSF grants AST-04-49809 and AST-05-06648.

  16. NASA F-15B #836 landing with Quiet Spike attached

    NASA Image and Video Library

    2006-10-03

    NASA F-15B #836 landing with Quiet Spike attached. The project seeks to verify the structural integrity of the multi-segmented, articulating spike attachment designed to reduce and control a sonic boom.

  17. The relationship between the human state and external perturbations of atmospheric, geomagnetic and solar origin

    NASA Astrophysics Data System (ADS)

    Gavryuseva, E.; Kroussanova, N.

    2002-12-01

    The relationship between the state of human body and the external factors such as the different phenomena of solar activity, geomagnetic perturbations and local atmospheric characteristics is studied. The monitoring of blood pressure and electro-conductivity of human body in acupuncture points for a group fo 28 people over the period of 1.5 year has been performed daily from February 2001 to August 2002 in Capodimonte Observatory in Naples, Italy. The modified Voll method of electropuncture diagnostics was used. The strong correlation between the human body state and meteo conditions is found and the probable correlation with geomagnetic perturbations is discussed.

  18. [Individual responses of arterial pressure to geomagnetic activity in practically healthy subjects].

    PubMed

    Zenchenko, T A; Dimitrova, S; Stoilova, I; Breus, T K

    2009-01-01

    Dynamic analysis of arterial blood pressure in relation to the Earth's magnetic field perturbations was performed in 77 practically healthy volunteers (staff of Bulgarian Academy of Sciences). Almost half of them proved magneto-sensitive, i.e. experienced AP elevation with increased geomagnetic activity. The probability of development of magnetic sensitivity was independent of age and gender but increased in volunteers having even mild cardiovascular pathology. These subjects complained of worsened health condition upon a rise in geomagnetic activity. However, some volunteers reported deteriorated well-being without AD elevation. It means that AD measurement may be insufficient for reliable monitoring magnetic sensitivity.

  19. A time-compressed simulated geomagnetic storm influences the nest-exiting flight angles of the stingless bee Tetragonisca angustula.

    PubMed

    Esquivel, D M S; Corrêa, A A C; Vaillant, O S; de Melo, V Bandeira; Gouvêa, G S; Ferreira, C G; Ferreira, T A; Wajnberg, E

    2014-03-01

    Insects have been used as models for understanding animal orientation. It is well accepted that social insects such as honeybees and ants use different natural cues in their orientation mechanism. A magnetic sensitivity was suggested for the stingless bee Schwarziana quadripunctata, based on the observation of a surprising effect of a geomagnetic storm on the nest-exiting flight angles. Stimulated by this result, in this paper, the effects of a time-compressed simulated geomagnetic storm (TC-SGS) on the nest-exiting flight angles of another stingless bee, Tetragonisca angustula, are presented. Under an applied SGS, either on the horizontal or vertical component of the geomagnetic field, both nest-exiting flight angles, dip and azimuth, are statistically different from those under geomagnetic conditions. The angular dependence of ferromagnetic resonance (FMR) spectra of whole stingless bees shows the presence of organized magnetic nanoparticles in their bodies, which indicates this material as a possible magnetic detector.

  20. A time-compressed simulated geomagnetic storm influences the nest-exiting flight angles of the stingless bee Tetragonisca angustula

    NASA Astrophysics Data System (ADS)

    Esquivel, D. M. S.; Corrêa, A. A. C.; Vaillant, O. S.; de Melo, V. Bandeira; Gouvêa, G. S.; Ferreira, C. G.; Ferreira, T. A.; Wajnberg, E.

    2014-03-01

    Insects have been used as models for understanding animal orientation. It is well accepted that social insects such as honeybees and ants use different natural cues in their orientation mechanism. A magnetic sensitivity was suggested for the stingless bee Schwarziana quadripunctata, based on the observation of a surprising effect of a geomagnetic storm on the nest-exiting flight angles. Stimulated by this result, in this paper, the effects of a time-compressed simulated geomagnetic storm (TC-SGS) on the nest-exiting flight angles of another stingless bee, Tetragonisca angustula, are presented. Under an applied SGS, either on the horizontal or vertical component of the geomagnetic field, both nest-exiting flight angles, dip and azimuth, are statistically different from those under geomagnetic conditions. The angular dependence of ferromagnetic resonance (FMR) spectra of whole stingless bees shows the presence of organized magnetic nanoparticles in their bodies, which indicates this material as a possible magnetic detector.

  1. 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

    The 2003 jerk has an abrupt change in the geomagnetic secular variation (SV), and was recognized as a local phenomenon of internal origin from the satellite observations (Olsen and Mandea, 2007). Notable strength of the 2003 jerk is located at Mid-Eastern Asia. The temporal and spatial features at this area are important to resolve the Earth's core fluid flow dynamics at local scale (e.g. Wardinski et al., 2008). We investigate the temporal-spatial development of the 2003 jerk in more detail at Mid-Eastern Asia with the ground-based observations and CHAOS-3 core field model. We select the data in the international geomagnetic quiet days to calculate the monthly means. In order to reduce the influence of the external field, we adopt a function comprising the terms associated with the indices of the geomagnetic activity, and the terms of the periodic signals on the observatory monthly means data (Stewart and Whaler, 1992). We then use an empirical AR-2 model to represent the internal field signals in the observatory data. The extreme detection is applied to identify the jerk in the SV time series. The onset time and the strength of the 2003 jerk are obtained through the detection for geomagnetic field component, X, Y and Z. The maximum of the strength of the 2003 jerk is located under the Indian mainland. The onset time of this jerk propagates approximately southeastward. Two jerks in 2001 and 2003 for the Z component are further compared and they are confirmed as independent processes. We suggest the jerk in 2001 identical to the well known 1999 jerk in Europe (Mandea et al., 2000). Our results reveal the fine structures of the 2003 jerk that corroborate the conclusions in previous studies. The larger scale time-spatial structure given by the AR-2 model constructed from ground observatory data (monthly values) is consistent with the results from the CHAOS-3 model. This structure can be applied for further inversion of the local core surface fluid flow motions

  2. 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.

  3. Use of Multivariate Relevance Vector Machines in forecasting multiple geomagnetic indices

    NASA Astrophysics Data System (ADS)

    Andriyas, T.; Andriyas, S.

    2017-02-01

    The forecasting ability of Multivariate Relevance Vector Machines (MVRVM), used previously to generate forecasts for the Dst index, is extended to forecast the Dst, AL, and PC indices during the years 1975-2007. Such learning machines are used in forecasting because of their robustness, efficiency, and sparseness. The MVRVM model was trained on solar wind and geomagnetic activity data sampled every hour with activity periods of various intensities, durations, and features. It was found that during the training phase, for a given error threshold, 14.60% of the training data was needed to explain the features of the data. The trained model was then tested on 177 different storm intervals, at various levels of geomagnetic activity, to generate simultaneous forecasts of the three indices at a lead time of one hour (1-h). The focus of the modeling was to assess the forecasts during main storm (MS) time periods when the indices show enhanced activity above quiet time values. The forecasts obtained by the MVRVM model reported in this paper returned a MS time average prediction efficiency, PE bar of 82.42%, 84.40%, and 76.00% and RMSE bar of 13.70 nT, 97.00 nT, and -0.77 mV/m, for the Dst, AL, and PC indices, respectively. The qualitative numbers indicated that the model underestimated the peak amplitude of the indices during the geomagnetic activity, but the peaks were forecasted on time by the model, on average. The forecasting results indicate a robust model generalization and the MVRVM's ability to learn the input-output relationship through a sparse model framework. A qualitative comparison with the previous univariate RVM forecast of Dst indicates that the model goodness of fit numbers improved in the present study.

  4. Eliminating large-scale magnetospheric current perturbations from long-term geomagnetic observatory data

    NASA Astrophysics Data System (ADS)

    Pick, L.; Korte, M. C.

    2016-12-01

    Magnetospheric currents generate the largest external contribution to the geomagnetic field observed on Earth. Of particular importance is the solar-driven effect of the ring current whose fluctuations overlap with internal field secular variation (SV). Recent core field models thus co-estimate this effect but their validity is limited to the last 15 years offering satellite data. We aim at eliminating magnetospheric modulation from the whole geomagnetic observatory record from 1840 onwards in order to obtain clean long-term SV that will enhance core flow and geodynamo studies.The ring current effect takes form of a southward directed external dipole field aligned with the geomagnetic main field axis. Commonly the Dst index (Sugiura, 1964) is used to parametrize temporal variations of this dipole term. Because of baseline instabilities, the alternative RC index was derived from hourly means of 21 stations spanning 1997-2013 (Olsen et al., 2014). We follow their methodology based on annual means from a reduced station set spanning 1960-2010. The absolute level of the variation so determined is "hidden" in the static lithospheric offsets taken as quiet-time means. We tackle this issue by subtracting crustal biases independently calculated for each observatory from an inversion of combined Swarm satellite and observatory data.Our index reproduces the original annual RC index variability with a reasonable offset of -10 nT in the reference time window 2000-2010. Prior to that it depicts a long-term trend consistent with the external dipole term from COV-OBS (Gillet et al., 2013), being the only long-term field model available for comparison. Sharper variations that are better correlated with the Ap index than the COV-OBS solution lend support to the usefulness of our initial modeling approach. Following a detailed sensitivity study of station choice future work will focus on increasing the resolution from annual to hourly means.

  5. Study of quiet turbofan STOL aircraft for short haul transportation

    NASA Technical Reports Server (NTRS)

    Higgins, T. P.; Stout, E. G.; Sweet, H. S.

    1973-01-01

    A study of quiet turbofan short takeoff aircraft for short haul air transportation was conducted. The objectives of the study were to: (1) define representative aircraft configurations, characteristics, and costs associated with their development, (2) identify critical technology and technology related problems to be resolved in successful introduction of representative short haul aircraft, (3) determine relationships between quiet short takeoff aircraft and the economic and social viability of short haul, and (4) identify high payoff technology areas.

  6. On the Solar Quiet Variation Measured in Latin America by the Embrace Magnetometer Network

    NASA Astrophysics Data System (ADS)

    Denardini, Clezio Marcos; Moro, Juliano; Araujo Resende, Laysa Cristina; Chen, Sony Su

    2016-07-01

    The present work show the first results of the study about the seasonal variation of the Solar quiet (Sq) Earth's magnetic field based on magnetic measurements from the Embrace Magnetic Network (MagNet) at several latitudes in South America, covering the equatorial and low latitudinal region. For this study, we used data covering the period from September 2010 to December 2015, during the ascending phase of the solar cycle 24. Before analyzing the magnetic data collected from the Embrace Magnet, we compared the magnetic data collected by the Embrace variometer installed at Vassouras-RJ, in Brazil, with the same data collected by the absolute magnetometer installed by the Intermagnet at the same observatory. We show that our data is in pretty good agreement to the absolute values. With respect to the seasonal variation, we show clear seasonal modulation in all components, irrespective the latitude. The H component analysis revealed to have a seasonal dependence in both aspects: the duration of positive excursion along the day and the maximum amplitude. And the other components have also shown remarkable regional characteristic of the variation of the Sq. Finally, we take these results as the first steps towards developing a Sq model to be superimposed to International Geomagnetic Reference Field (IGRF) model as a useful tool for space weather forecast.

  7. Solar quiet current response in the African sector due to a 2009 sudden stratospheric warming event

    NASA Astrophysics Data System (ADS)

    Bolaji, O. S.; Oyeyemi, E. O.; Owolabi, O. P.; Yamazaki, Y.; Rabiu, A. B.; Okoh, D.; Fujimoto, A.; Amory-Mazaudier, C.; Seemala, G. K.; Yoshikawa, A.; Onanuga, O. K.

    2016-08-01

    We present solar quiet (Sq) variation of the horizontal (H) magnetic field intensity deduced from Magnetic Data Acquisition System (MAGDAS) records over Africa during an unusual strong and prolonged 2009 sudden stratospheric warming (SSW) event. A reduction in the SqH magnitude that enveloped the geomagnetic latitudes between 21.13°N (Fayum FYM) in Egypt and 39.51°S (Durban DRB) in South Africa was observed, while the stratospheric polar temperature was increasing and got strengthened when the stratospheric temperature reached its maximum. Another novel feature associated with the hemispheric reduction is the reversal in the north-south asymmetry of the SqH, which is indicative of higher SqH magnitude in the Northern Hemisphere compared to the Southern Hemisphere during SSW peak phase. The reversal of the equatorial electrojet (EEJ) or the counter electrojet (CEJ) was observed after the polar stratospheric temperature reached its maximum. The effect of additional currents associated with CEJ was observed in the Southern Hemisphere at middle latitude. Similar changes were observed in the EEJ at the South America, Pacific Ocean, and Central Asia sectors. The effect of the SSW is largest in the South American sector and smallest in the Central Asian sector.

  8. 49 CFR 222.39 - How is a quiet zone established?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Quiet Zone Risk Index is at, or below, the Nationwide Significant Risk Threshold, as follows: (i) If the Quiet Zone Risk Index is already at, or below, the Nationwide Significant Risk Threshold without being... Quiet Zone Risk Index to a level at, or below, the Nationwide Significant Risk Threshold. (3) A quiet...

  9. Bilateral vibrant soundbridge implantation: audiologic and subjective benefits in quiet and noisy environments.

    PubMed

    Garin, Pierre; Schmerber, Sébastien; Magnan, Jacques; Truy, Eric; Uziel, Alain; Triglia, Jean-Michel; Bebear, Jean-Pierre; Labassi, Samia; Lavieille, Jean-Pierre

    2010-12-01

    The results support bilateral sequential implantation for patients who are not completely satisfied after implantation of one side. To evaluate the benefit of bilateral Vibrant Soundbridge middle ear implantation as compared with unilateral implantation in quiet and noisy environments. This was a multicentric and retrospective study of 15 patients with symmetrical sensorineural hearing loss who were implanted sequentially in both ears. The performance of each subject was compared under three conditions: with the right implant activated, with the left implant activated, and with both implants activated. Audiometric tests were compared with self-assessment subjective evaluation by questionnaire. Both qualitative and quantitative assessments demonstrated improvement in speech intelligibility, especially in background noise, but also for low voice intensity in quiet.

  10. Flight Test Results on the Stability and Control of the F-15B Quiet Spike Aircraft

    NASA Technical Reports Server (NTRS)

    Moua, Cheng; McWherter, Shaun H.; Cox, Timothy H.; Gera, Joseph

    2007-01-01

    The Quiet Spike (QS) flight research program was an aerodynamic and structural proof-of-concept of a telescoping sonic-boom suppressing nose boom on an F-15 B aircraft. The program goal was to collect flight data for model validation up to 1.8 Mach. The primary test philosophy was maintaining safety of flight. In the area of stability and controls the primary concerns were to assess the potential destabilizing effect of the spike on the stability, controllability, and handling qualities of the aircraft and to ensure adequate stability margins across the entire QS flight envelop. This paper reports on the stability and control methods used for flight envelope clearance and flight test results of the F-15B Quiet Spike. Also discussed are the flight test approach, the criteria to proceed to the next flight condition, brief pilot commentary on typical piloting tasks, approach and landing, and refueling task, and air data sensitivity to the flight control system.

  11. STUDY OF CALIBRATION OF SOLAR RADIO SPECTROMETERS AND THE QUIET-SUN RADIO EMISSION

    SciTech Connect

    Tan, Chengming; Yan, Yihua; Tan, Baolin; Fu, Qijun; Liu, Yuying; Xu, Guirong

    2015-07-20

    This work presents a systematic investigation of the influence of weather conditions on the calibration errors by using Gaussian fitness, least chi-square linear fitness, and wavelet transform to analyze the calibration coefficients from observations of the Chinese Solar Broadband Radio Spectrometers (at frequency bands of 1.0–2.0 GHz, 2.6–3.8 GHz, and 5.2–7.6 GHz) during 1997–2007. We found that calibration coefficients are influenced by the local air temperature. Considering the temperature correction, the calibration error will reduce by about 10%–20% at 2800 MHz. Based on the above investigation and the calibration corrections, we further study the radio emission of the quiet Sun by using an appropriate hybrid model of the quiet-Sun atmosphere. The results indicate that the numerical flux of the hybrid model is much closer to the observation flux than that of other ones.

  12. Models of the quiet and active solar atmosphere from Harvard OSO data.

    NASA Technical Reports Server (NTRS)

    Noyes, R. W.

    1971-01-01

    Review of some Harvard Observatory programs aimed at defining the physical conditions in quiet and active solar regions on the basis of data obtained from the OSO-IV and OSO-VI spacecraft. The spectral range covered is from 300 A to 1400 A. This spectral range consists of emission lines and continua from abundant elements such as hydrogen, helium, carbon, nitrogen, oxygen, silicon, magnesium, aluminum, neon, iron, and calcium in various ionization states ranging from neutral to 15 times ionized. The structure is discussed of the quiet solar atmosphere as deduced from center-to-limb behavior of spectral lines and continua formed in the chromosphere and corona. In reviewing investigations of solar active regions, it is shown that the structure of these regions varies in a complicated manner from point to point. The local structure is influenced by factors such as the magnetic field configuration within the active region and the age or evolutionary state of the region.

  13. Detection of Auditory Signals in Quiet and Noisy Backgrounds while Performing a Visuo-spatial Task

    PubMed Central

    Rawool, Vishakha W.

    2016-01-01

    Context: The ability to detect important auditory signals while performing visual tasks may be further compounded by background chatter. Thus, it is important to know how task performance may interact with background chatter to hinder signal detection. Aim: To examine any interactive effects of speech spectrum noise and task performance on the ability to detect signals. Settings and Design: The setting was a sound-treated booth. A repeated measures design was used. Materials and Methods: Auditory thresholds of 20 normal adults were determined at 0.5, 1, 2 and 4 kHz in the following conditions presented in a random order: (1) quiet with attention; (2) quiet with a visuo-spatial task or puzzle (distraction); (3) noise with attention and (4) noise with task. Statistical Analysis: Multivariate analyses of variance (MANOVA) with three repeated factors (quiet versus noise, visuo-spatial task versus no task, signal frequency). Results: MANOVA revealed significant main effects for noise and signal frequency and significant noise–frequency and task–frequency interactions. Distraction caused by performing the task worsened the thresholds for tones presented at the beginning of the experiment and had no effect on tones presented in the middle. At the end of the experiment, thresholds (4 kHz) were better while performing the task than those obtained without performing the task. These effects were similar across the quiet and noise conditions. Conclusion: Detection of auditory signals is difficult at the beginning of a distracting visuo-spatial task but over time, task learning and auditory training effects can nullify the effect of distraction and may improve detection of high frequency sounds. PMID:27991458

  14. 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

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

    SciTech Connect

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

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  18. Changes of the Sq Quiet Daily Variations of the Geomagnetic Field as a Function of Time of Year and Latitude,

    DTIC Science & Technology

    1981-01-01

    obtained at Huancayo , Honolulu, and Baker Lake. The mean and median values of the correlation coefficient, all stations considered, were (respectively...percentage errors for all three components combined whereas, Huancayo , Tatuoca, Tucson, and Baker Lake show reasonably low all all-over values of...best, Paramaribo and Fredericksburg are very good, and Huancayo and Baker Lake are good. For future studies on induced effects of Sq these five

  19. Aeroelastic Calculations of Quiet High- Speed Fan Performed

    NASA Technical Reports Server (NTRS)

    Bakhle, Milind A.; Srivastava, Rakesh; Mehmed, Oral; Min, James B.

    2002-01-01

    An advanced high-speed fan was recently designed under a cooperative effort between the NASA Glenn Research Center and Honeywell Engines & Systems. The principal design goals were to improve performance and to reduce fan noise at takeoff. Scale models of the Quiet High-Speed Fan were tested for operability, performance, and acoustics. During testing, the fan showed significantly improved noise characteristics, but a self-excited aeroelastic vibration known as flutter was encountered in the operating range. Flutter calculations were carried out for the Quiet High-Speed Fan using a three-dimensional, unsteady aerodynamic, Reynolds-averaged Navier-Stokes turbomachinery code named "TURBO." The TURBO code can accurately model the viscous flow effects that can play an important role in various aeroelastic problems such as flutter with flow separation, flutter at high loading conditions near the stall line (stall flutter), and flutter in the presence of shock and boundary-layer interaction. Initially, calculations were performed with no blade vibrations. These calculations were at a constant rotational speed and a varying mass flow rate. The mass flow rate was varied by changing the backpressure at the exit boundary of the computational domain. These initial steady calculations were followed by aeroelastic calculations in which the blades were prescribed to vibrate harmonically in a natural mode, at a natural frequency, and with a fixed interblade phase angle between adjacent blades. The AE-prep preprocessor was used to interpolate the in-vacuum mode shapes from the structural dynamics mesh onto the computational fluid dynamics mesh and to smoothly propagate the grid deformations from the blade surface to the interior points of the grid. The aeroelastic calculations provided the unsteady aerodynamic forces on the blade surface due to blade vibrations. These forces were vector multiplied with the structural dynamic mode shape to calculate the work done on the blade during

  20. 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.