WorldWideScience

Sample records for optical observations geomagnetically

  1. Geomagnetic Observations and Models

    CERN Document Server

    Mandea, Mioara

    2011-01-01

    This volume provides comprehensive and authoritative coverage of all the main areas linked to geomagnetic field observation, from instrumentation to methodology, on ground or near-Earth. Efforts are also focused on a 21st century e-Science approach to open access to all geomagnetic data, but also to the data preservation, data discovery, data rescue, and capacity building. Finally, modeling magnetic fields with different internal origins, with their variation in space and time, is an attempt to draw together into one place the traditional work in producing models as IGRF or describing the magn

  2. Geomagnetic Observations for Main Field Studies

    DEFF Research Database (Denmark)

    Matzka, Jürgen; Chulliat, A.; Mandea, M.

    2010-01-01

    Direct measurements of the geomagnetic field have been made for more than 400 years, beginning with individual determinations of the angle between geographic and magnetic North. This was followed by the start of continuous time series of full vector measurements at geomagnetic observatories and t...... for magnetic field measurements on ground and in space and covers geomagnetic observatories, repeat stations, automatic observatories, satellites and historic observations. Special emphasis is laid on the global network of geomagnetic observatories....... and the beginning of geomagnetic repeat stations surveys in the 19th century. In the second half of the 20th century, true global coverage with geomagnetic field measurements was accomplished by magnetometer payloads on low-Earth-orbiting satellites. This article describes the procedures and instruments...

  3. Geomagnetic observations on Tristan da Cunha, South Atlantic Ocean

    DEFF Research Database (Denmark)

    Matzka, J.; Olsen, Nils; Maule, C. F.

    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 degrees 05' S, 12 degrees 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...... and operate a magnetometer station on Tristan da Cunha during the Swarm magnetic satellite mission (2011-2014)....

  4. Radio and optical observations of large-scale traveling ionospheric disturbances during a strong geomagnetic storm of 6-8 April 2000

    CERN Document Server

    Afraimovich, E L; Leonovich, L A; Lesyuta, O S; Mikhalev, A V; Ashkaliev, Y F; Aushev, V M; Vodyannikov, V V; Yakovets, A F; Ashkaliev, Ya. F.

    2001-01-01

    Basic properties of the mid-latitude large-scale traveling ionospheric disturbances (LS TIDs) during the maximum phase of a strong magnetic storm of 6-8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics, (51.9 deg. N, 103.0 deg. E) and MORTI located at the observatory of the Institute of Ionosphere (43.2 deg. N, 77.0 deg. E). Observations of the O (557.7 nm, 630.0 nm, 360-410 nm, and 720-830 nm) emissions originating from atmospheric layers centered at altitudes of 90 km, 97 km, and 250 km were carried out at Irkutsk and of the O_2 (866.5 nm) emission originating from an atmospheric layer centered at altitude of 95 km was carried out at Almaty. Variations of the f_0F2 and virtual altitude of the F2 layer were measured at Al...

  5. Calibration of historical geomagnetic observations from Prague-Klementinum

    Science.gov (United States)

    Hejda, Pavel

    2015-04-01

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

  6. Re-Evaluation of Geomagnetic Field Observation Data at Syowa Station, Antarctica

    Directory of Open Access Journals (Sweden)

    K Takahashi

    2013-05-01

    Full Text Available The Japanese Antarctic Research Expedition has conducted geomagnetic observations at Syowa Station, Antarctica, since 1966. Geomagnetic variation data measured with a fluxgate magnetometer are not absolute but are relative to a baseline and show drift. To enhance the importance of the geomagnetic data at Syowa Station, therefore, it is necessary to correct the continuous variation data by using absolute baseline values acquired by a magnetic theodolite and proton magnetometer. However, the database of baseline values contains outliers. We detected outliers in the database and then converted the geomagnetic variation data to absolute values by using the reliable baseline values.

  7. High resolution geomagnetic field observations at Terra Nova bay, Antarctica

    Directory of Open Access Journals (Sweden)

    P. Palangio

    1996-06-01

    Full Text Available he preliminary results obtained from the analysis in the micropulsation frequency range of high time resolution magnetic field data recorded at the Antarctic Italian geomagnetic observatory at Terra Nova Bay for 11 consecutive days in February 1994 are reported. The spectral index over the whole Pcl-Pc5 frequency range is of the order of 3.5 and its value significantly increases beyond about 50 mHz. Spectral peaks in the Pc3 frequency range are common, especially during the daytime hours, and are probably due to the direct penetration of upstream waves in the cusp region. From the local time distribution of the micro pulsation power, a signifi - cant activity enhancement around the local magnetic noon emerges, in agreement with previous observations. The analysis of the signal polarisation characteristics in the horizontal plane shows a predominant CW polarisation in the Pcl-Pc3 frequency ranges with the major axis of the polarisation ellipse in the first quadrant.

  8. New insights on geomagnetic storms from observations and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Jordanova, Vania K [Los Alamos National Laboratory

    2009-01-01

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

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

    Science.gov (United States)

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

    2015-10-01

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

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

    Science.gov (United States)

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

    2013-04-01

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

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

    Science.gov (United States)

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

    2017-06-01

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

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

    Science.gov (United States)

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

    2017-01-01

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

  13. Identification of possible intense historical geomagnetic storms using combined sunspot and auroral observations from East Asia

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    2005-03-01

    Full Text Available Comprehensive catalogues of ancient sunspot and auroral observations from East Asia are used to identify possible intense historical geomagnetic storms in the interval 210 BC-AD 1918. There are about 270 entries in the sunspot catalogue and about 1150 entries in the auroral catalogue. Special databases have been constructed in which the scientific information in these two catalogues is placed in specified fields. For the purposes of this study, an historical geomagnetic storm is defined in terms of an auroral observation that is apparently associated with a particular sunspot observation, in the sense that the auroral observation occurred within several days of the sunspot observation. More precisely, a selection criterion is formulated for the automatic identification of such geomagnetic storms, using the oriental records stored in the sunspot and auroral databases. The selection criterion is based on specific assumptions about the duration of sunspot visibility with the unaided eye, the likely range of heliographic longitudes of an energetic solar feature, and the likely range of transit times for ejected solar plasma to travel from the Sun to the Earth. This selection criterion results in the identification of nineteen putative historical geomagnetic storms, although two of these storms are spurious in the sense that there are two examples of a single sunspot observation being associated with two different auroral observations separated by more than half a (synodic solar rotation period. The literary and scientific reliabilities of the East Asian sunspot and auroral records that define the nineteen historical geomagnetic storms are discussed in detail in a set of appendices. A possible time sequence of events is presented for each geomagnetic storm, including possible dates for both the central meridian passage of the sunspot and the occurrence of the energetic solar feature, as well as likely transit times for the ejected solar plasma

  14. Analysis on observational results of Pi2 geomagnetic pulsation in Henan region

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A measurement profile consisted of 5 sites from Xinyang to Tangyin in Henan Province was set up in September of 1996 to carry out simultaneous observation of Pi2 geomagnetic pulsations. Simultaneity of Pi2 geomagnetic pulsation occurrence along the N-S profile was investigated. Results of analysis pointed out that Pi2 geomagnetic pulsations appeared at first at the site of Xinyang at the southern end of the profile, the later the same Pi2 geomagnetic pulsation appeared, the more north the site was at. Apparent propagation speed of Pi2 in N-S direction in the region is about 140 km/s. Because Pi2 geomagnetic pulsation varying with time is of instability, and based on characteristics that basic wavelet can be dilated and localized, we selected proper basic wavelet form and by means of wavelet transform to analyze the changes of periods and amplitudes of main periodic components included in Pi2 pulsations with time. The results show that there existed complex form in periods and amplitudes of wavelet varying with time.

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

    Science.gov (United States)

    Kuang, Weijia; Tangborn, Andrew

    2014-01-01

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

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

    Science.gov (United States)

    Ruzhin, Yuri; Kamogawa, Masashi; Novikov, Victor

    statistical approach for the problem of ionosphere-lithosphere coupling, and in each case the possible behavior of fluids should be considered under electromagnetic impact on lithosphere. Experimental results supporting this idea are obtained at the spring-block model simulating the seismic cycle (slow accumulation and sharp drop of stresses in the fault gauge), as well as from field observations of water level variations in the well during ionospheric disturbances are presented and discussed. In the lab experiments it was shown that the earthquake may be triggered by very small fluid content injected into the simulated fault (earthquake activity and geomagnetic Sq-variations // Natural Hazards and Earth System Sciences, 3, 2003, p.p.171-177. 2. Novikov V.A. Water imbalance in the geological fault as a possible earthquake trigger // AGU 2012 Fall Meeting, Dec. 3-8, San Francisco, USA, Abstract GC42B-08.

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

    Directory of Open Access Journals (Sweden)

    C. R. Wilford

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

  18. Geomagnetism applications

    Science.gov (United States)

    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.

  19. Geomagnetic Secular Variation in Texas over the Last 17,000 Years: High-Intensity Geomagnetic Field 'Spike' Observed at ca. 3000 cal BP

    Science.gov (United States)

    Bourne, M. D.; Feinberg, J. M.; Waters, M. R.; Stafford, T. W., Jr.; Forman, S. L.; Lundelius, E. L.

    2015-12-01

    By observing the fluctuations in direction and intensity of the Earth's magnetic field through time, we increase our understanding of the fluid motions in the Earth's outer core that sustain the geomagnetic field, the geodynamo. Recent archaeomagnetic studies in the Near East have proposed extremely rapid increases - 'spikes' - in geomagnetic field intensity ca. 3000 years ago that have proved problematic for our current understanding of core-flow. However, until now, these geomagnetic spikes had not been observed outside of the Near East, where they have been found in metallurgical slag and mud brick walls. We present a new fully-oriented, geomagnetic secular variation and relative palaeointensity (RPI) record for the last 17,000 years from Hall's Cave, Texas. Sediment washed into the cave has formed a continuous stratigraphic sequence that is at least 3.5 m thick. Within the stable, cool climate of the cave, pedogenic and bioturbation processes are almost non-existent, thereby limiting post-depositional physical and geochemical alteration of the magnetic record. The sub-aerial and subterranean setting of the sedimentary sequence in Hall's Cave enabled us to collect oriented palaeomagnetic cubes from an excavated section through the sequence. The palaeomagnetic samples yielded high-quality vectors. An age model for the sequence, determined using 57 AMS 14C-dates on individual bones from microvertebrate, was combined with the palaeomagnetic data to construct a secular variation record. The record is in broad agreement with predictions by Holocene field models for the site's location. However, at ca. 3000 years ago, the RPI data indicate an almost four-fold increase in geomagnetic field intensity lasting several hundred years and contemporaneous with the more short-lived, decadal-scale spikes reported from the Near East. Evidence for this extreme intensity event outside of the Near East has major implications for our current understanding of core-dynamics.

  20. Statistical correlation of low-altitude ENA emissions with geomagnetic activity from IMAGE/MENA observations

    Science.gov (United States)

    Mackler, D. A.; Jahn, J.-M.; Perez, J. D.; Pollock, C. J.; Valek, P. W.

    2016-03-01

    Plasma sheet particles transported Earthward during times of active magnetospheric convection can interact with exospheric/thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low-altitude (300-800 km) ion precipitation in the high-latitude atmosphere/ionosphere are termed low-altitude emissions (LAEs). Remotely observed LAEs are highly nonisotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90°. The Geomagnetic Emission Cone of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity. The LAE data are from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000-2005). The SYM-H, AE, and Kp indices are used to describe geomagnetic activity. The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM-H showing the greatest sensitivity. The magnetic local time distribution of LAEs is centered about midnight and spreads with increasing activity. The invariant latitude for all indices has a slightly negative correlation. The combined results indicate LAE behavior similar to that of ion precipitation.

  1. Improving our knowledge of the rapid geomagnetic field intensity variation observed in Europe around 800 AD

    Science.gov (United States)

    Gómez-Paccard, M.; Chauvin, A.; Lanos, P.; Dufresne, P.; Kovacheva, M.; Hill, M. J.; Beamud, E.; Gutiérrez-Lloret, S.; Cañavate, V.; Blain, S.; Bouvier, A.; Oberlin, C.; Guibert, P.; Sapin, C.; Pringent, D.

    2011-12-01

    Available European data indicate that during the past 2500 years there have been periods of rapid intensity geomagnetic fluctuations interspersed with periods of little change. The challenge now is to precisely describe these rapid changes. The aim of this study is to obtain an improved description of the sharp geomagnetic intensity change that took place in Western Europe around 800 yrs AD as well as to investigate if this peak is observed at a continental scale. For this purpose 13 precisely dated early medieval Spanish pottery fragments, 4 archeological French kilns and a 3 collections of bricks used for the construction of different historical buildings from France and with ages ranging between 330 to 1290 AD have been studied. The material collected has been dated by archeological/historical constraints together with radiocarbon,thermoluminiscence (TL) and archeomagentic analysis. From classical Thellier experiments including TRM anisotropy and cooling rate corrections upon archeointensity estimates and conducted on 164 specimens (119 of them giving reliable results) ten new high-quality mean intensities have been obtained. The new intensity data together with a selection of the most reliable data from Western Europe have been relocated to the latitude of Paris and confirm the existence of an intensity maxima of ~85 μT centred at ~850 AD and related to intensity changes up to 20 μT per century. The results also indicate that a previous abrupt intensity change (reaching a maximum value of ~ 90 μT) took place in Western Europe around 650 AD. A selection of high-quality intensity data from Bulgaria, Italy and Greece indicate a very similar intensity trend for Eastern Europe. Although available data indicate that the duration of such periods of high intensities may be of less than one century more data are needed to infer the exact duration of these maximums. A comparison between the selected data and regional and global geomagnetic field models indicates that

  2. Geomagnetic storms during the last decade: Cluster and Double Star observations (Invited)

    Science.gov (United States)

    Escoubet, C.; Taylor, M. G.; Masson, A.; Laakso, H. E.; Liu, Z.; Goldstein, M. L.

    2013-12-01

    The launch of the Cluster spacecraft almost coincided with one of the largest geomagnetic storm of the last decade, well known as the "Bastille Day" storm, on 14-15 July 2000. Planned on 15 July, the launch was aborted a few minutes before due to a thunderstorm that had hit the Baikonour cosmodrome and made a disruption in the communication lines with the rocket. The launch took place the day after, on 16 July 2000. Our US colleagues had warned us about the storm and recommended not to launch on 15 July. Given the facts that (1) Cluster was built to study the effects of space weather and geomagnetic storms and (2) that the Russian launch authorities were not concerned for the Soyuz rocket, it was decided to go ahead with the launch. The launch was fine and, after a second launch less than a month later, the four Cluster spacecraft were put successfully in their 4x19 RE polar orbit. Since then, Cluster has observed many geomagnetic storms and could observe, for the first time with a constellation of four spacecraft, the dynamics induced in the magnetosphere by coronal mass ejections or interplanetary shocks coming from the Sun. In this talk we will use storms observed by Cluster and Double Star in the last decade to illustrate how the magnetosphere was affected. We have observed large compressions of the magnetosphere, distortions of the polar cusp, acceleration of particles associated with chorus and ULF waves, intensification of the ring current imaged by energetic neutral atom imagers, oxygen outflow from polar regions, and tail current sheet motions.

  3. Ground based observations of Pc3-Pc5 geomagnetic pulsation power at Antarctic McMurdo station

    Directory of Open Access Journals (Sweden)

    C. G. Maclennan

    1998-06-01

    Full Text Available The two horizontal geomagnetic components and, measured by a fluxgate magnetometer at Antarctic McMurdo station (corrected geomagnetic coordinates 80.0° S, 327.5° E, are analyzed for the period May-June 1994; the spectral powers are calculated and integrated over three frequency intervals corresponding to the nominal ranges. The time dependence of those integrated powers and their correlations with northern auroral indices and solar wind speed are considered. The observations are compared with previous results reported from Terra Nova Bay station (located near McMurdo at the same corrected geomagnetic latitude during Antarctic summer intervals. The differences found between the two stations are discussed in terms of the seasonal dependence of geomagnetic field line configurations in the near cusp region.

  4. The 2014 geomagnetic jerk as observed by southern African magnetic observatories

    Science.gov (United States)

    Kotzé, P. B.

    2017-01-01

    Rapid secular variation pulses in the Earth's geomagnetic field have been identified during the last decade. In particular, the 2014 jerk is the latest in a series of localised rapid secular variation events observed at the Earth's surface which are thought to be the result of rapid oscillations at the core surface approximately at a depth of 3000 km. In Southern Africa, the 2014 jerk has been analysed using data from four observatories located at Hermanus, Hartebeesthoek, Keetmanshoop and Tsumeb and found that this event occurred with varying strengths in the different components at a particular observatory, while different observatories in the region showed strong individual characteristics. The changes in the secular variation patterns at individual magnetic observatories in this study took place in an area characterised by rapid changes in the geomagnetic field with time. Of particular interest is that global field models like CHAOS-6 and POMME 10 derived from various combinations of ground and satellite data do not always indicate similar short-period patterns in X, Y and Z as revealed by observatory measurements. This has been confirmed by comparing the secular variation pattern at the Kourou magnetic observatory located in French Guiana, a station close to the current centre of the South Atlantic Anomaly.

  5. Voyager observations in the distant heliosheath: An analogy with ISEE-3 observations in the deep geomagnetic tail

    OpenAIRE

    Richardson, Ian G.

    2016-01-01

    We suggest an analogy between energetic particle and magnetic field observations made by the Voyager 1 spacecraft in the distant heliosheath at 122 AU in August 2012, and those made in the distant geomagnetic tail by the ISEE 3 spacecraft in 1982-1983, despite large differences in the time and distance scales. The analogy suggests that in August, 2012, Voyager 1 may not have moved from the anomalous cosmic ray (ACR)-dominated heliosheath into the interstellar medium but into a region equivale...

  6. Voyager observations in the distant heliosheath: An analogy with ISEE-3 observations in the deep geomagnetic tail

    Science.gov (United States)

    Richardson, Ian G.

    2017-08-01

    We suggest an analogy between energetic particle and magnetic field observations made by the Voyager 1 spacecraft in the distant heliosheath at 122 AU in August 2012, and those made in the distant geomagnetic tail by the ISEE 3 spacecraft in 1982-1983, despite large differences in the time and distance scales. The analogy suggests that in August, 2012, Voyager 1 may not have moved from the anomalous cosmic ray (ACR)-dominated heliosheath into the interstellar medium but into a region equivalent to the ;lobes; of the geomagnetic tail, composed of heliospheric field lines which have reconnected with the interstellar medium beyond the spacecraft and so are open to the entry of cosmic rays, while heliospheric particles (e.g., ACRs) are free to escape, and which maintain a ∼Parker spiral configuration. The heliopause, analogous to the magnetopause forming the outer boundary of the lobes, may then lie beyond this so-called ;heliocliff;. Even if this analogy is incorrect, the remarkable similarities between the energetic particle and magnetic field observations in these very different regions are worth noting.

  7. Equatorial Ionospheric Irregularities Observed in the South American Sector During the December 2006 Geomagnetic Storm

    Science.gov (United States)

    Sahai, Y.; de Jesus, R.; Guarnieri, F. L.; Fagundes, P. R.; de Abreu, A. J.; Becker-Guedes, F.; Abalde, J. R.; Brunini, C.; Gende, M.; Cintra, T.; de Souza, V.; Pillat, V.; Lima, W.

    2009-05-01

    This investigation presents studies related to the observations of equatorial ionospheric irregularities in the ionospheric F-region in the South American sector during the intense geomagnetic storm in December 2006, during the period of low solar activity. The geomagnetic storm reached a minimum Dst of -147 nT at 0700 UT on 15 December. In this work ionospheric sounding data obtained between 13 and 16 December 2006 at Palmas (PAL; 10.2o S, 48.2o W; dip latitude 6.6o S) and São José dos Campos (SJC, 23.2o S, 45.9o W; dip latitude 17.6o S), Brazil, and Jicamarca (JIC, 12.0o S, 76.8o W; dip latitude 0.05o S), Peru, have been used. Also, vertical total electron content (VTEC) and phase fluctuations (TECU/min) from GPS observations obtained at Brasilia (BRAZ, 15.9o S, 47.9o W; dip latitude 11.7o S), Presidente Prudente (PPTE, 22.12° S, 51.4° W; dip latitude 14,9° S), Curitiba (PARA, 25.43o S, 49.21o W; dip latitude 18.4o S), Santa Maria (SMAR, 29.71o S, 53.07o W; dip latitude 19.6o S), Brazil, Bahia Blanca (VBCA, 38.7o S, 62.3o W; dip latitude 22.4o S) and Puerto Deseado (PDES, 47.7o S, 65.9o W, dip latitude 27.1o S), Argentina, during the period 13 to 16 December are presented. An unusual uplifting of the F-region during pre-reversal enhancement (PRE) on 14 December was possibly associated with a prompt penetration of electric field of magnetospheric origin after the storm sudden commencement (1414 UT on 14 December). On this geomagnetically disturbed night of 14-15 December, intense equatorial ionospheric irregularities were observed up to southern most GPS station PDES in Argentina. It should be mentioned that on the other nights viz., 12-13 and 13-14 December (both nights before the storm), and 15-16 December (recovery phase), the ionospheric irregularities are limited to only the Brazilian GPS stations. On the geomagnetically disturbed night of 14-15 December, strong oscillations were observed in the F-region base height possibly associated with Joule heating

  8. A new investigation on drift of base-line value in geomagnetic observation

    Science.gov (United States)

    Yang, Dong-Mei; Gao, Yu-Fen; Zhao, Yong-Fen; Huang, Wei-Bei

    1997-07-01

    A new explanation on drift of base-line (BL) value in geomagnetic observation was presented by means of detailed analysis on BL value of H-variometer at Tianshui Observatory from 1991 to 1995, in association with some numerical simulation. It was confirmed that drift does not always exist. For variometers running normally for many years, drift appears to be zero. The temperature-dependence of BL value is reversible below a certain temperature but irreversible above it. This irreversibility is the main reason that causes the BL value to show a monotonous declination with time, which has been mistaken for the drift in the past. As to the H-variometer at Tianshui Observatory, no drift exists in BL value in these years. A new method was introduced to study the BL value variation with temperature by separating it into three parts.

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

    Science.gov (United States)

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

    2015-09-01

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

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

    Science.gov (United States)

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

    2015-09-01

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

  11. A case for variational geomagnetic data assimilation: insights from a one-dimensional, nonlinear, and sparsely observed MHD system

    CERN Document Server

    Fournier, Alexandre; Alboussière, Thierry

    2007-01-01

    Secular variations of the geomagnetic field have been measured with a continuously improving accuracy during the last few hundred years, culminating nowadays with satellite data. It is however well known that the dynamics of the magnetic field is linked to that of the velocity field in the core and any attempt to model secular variations will involve a coupled dynamical system for magnetic field and core velocity. Unfortunately, there is no direct observation of the velocity. Independently of the exact nature of the above-mentioned coupled system -- some version being currently under construction -- the question is debated in this paper whether good knowledge of the magnetic field can be translated into good knowledge of core dynamics. Furthermore, what will be the impact of the most recent and precise geomagnetic data on our knowledge of the geomagnetic field of the past and future? These questions are cast into the language of variational data assimilation, while the dynamical system considered in this pape...

  12. Voyager observations in the distant heliosheath: An analogy with ISEE-3 observations in the deep geomagnetic tail

    CERN Document Server

    Richardson, Ian G

    2016-01-01

    We suggest an analogy between energetic particle and magnetic field observations made by the Voyager 1 spacecraft in the distant heliosheath at 122 AU in August 2012, and those made in the distant geomagnetic tail by the ISEE 3 spacecraft in 1982-1983, despite large differences in the time and distance scales. The analogy suggests that in August, 2012, Voyager 1 may not have moved from the anomalous cosmic ray (ACR)-dominated heliosheath into the interstellar medium but into a region equivalent to the "lobes" of the geomagnetic tail, composed of heliospheric field lines which have reconnected with the interstellar medium beyond the spacecraft and so are open to the entry of cosmic rays, while heliospheric particles (e.g., ACRs) are free to escape, and which maintain a ~Parker spiral configuration. The heliopause, analogous to the magnetopause forming the outer boundary of the lobes, may then lie beyond this so-called "heliocliff". Even if this analogy is incorrect, the remarkable similarities between the ener...

  13. Multi-Instrument Observations of Geomagnetic Storms in the Arctic Ionosphere

    DEFF Research Database (Denmark)

    Durgonics, Tibor; Komjathy, Attila; Verkhoglyadova, Olga;

    We present a multi-instrumented approach for the analysis of the Arctic ionosphere during the 19 February 2014 highly complex, multiphase geomagnetic storm. The geomagnetic storm was the result of two powerful and subsequent Earth-directed coronal mass ejections (CMEs). The first one was launched...... from the solar corona on 16 February and the second one on 18 February. We focus on effects of such solar-originated geomagnetic disturbances on the high latitude ionosphere because our present understanding of the fundamental ionospheric processes – particularly during perturbed times – in this region...

  14. Voyager Observations in the Distant Heliosheath - an Analogy With ISEE-3 Observations in theDeep Geomagnetic Tail

    Science.gov (United States)

    Richardson, Ian

    2015-04-01

    We suggest an analogy between energetic particle and magnetic field observations made by the Voyager 1 spacecraft in the distant heliosheath at 122 AU in August 2012 and those made in the distant geomagnetic tail by the Energetic Particle Anisotropy Spectrometer (EPAS) on the ISEE 3 spacecraft in 1982-1983, including remarkable similarities in the behavior of the energetic particle intensities and anisotropies despite large differences in the time and distance scales.The analogy suggests that Voyager 1 may have moved not into the interstellar medium from heliosheath but instead into a region equivalent to the “lobes” of the geomagnetic tail. This region may be composed of heliospheric field lines which have reconnected with the interstellar medium beyond the spacecraft and so are open to the entry of cosmic rays, while heliospheric particles (e.g., Anomalous Cosmic Rays) are free to escape, leaving only a weak population of large pitch-angle ACRs with “pancake” distributions similar to those also seen by ISEE 3 in the lobes of the tail. If this is the case, the actual heliopause (equivalent to the magnetopause), where the ambient interstellar medium is entered, lies beyond the current distance of Voyager 1.Temporary variations in the energetic particle and magnetic field intensities at Voyager over a period of around 27 days prior to the final boundary crossing are interpreted as the boundary twice approaching Voyager 1 and then retreating Sunward before the final crossing occurred. Similar features were frequently observed in the deep tail due to tail dynamics and “flapping” in the solar wind. The 27 day interval suggests that rotation of the heliosphere may have contributed to this boundary motion.Energetic particles in the tail are accelerated by reconnection in the plasma sheet which can lead to the formation of plasmoids. Both are elements of some recent models of the heliopause.

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

    Science.gov (United States)

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

    2014-09-01

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

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

    Science.gov (United States)

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

    1996-01-01

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

  17. A case for variational geomagnetic data assimilation: insights from a one-dimensional, nonlinear, and sparsely observed MHD system

    Directory of Open Access Journals (Sweden)

    A. Fournier

    2007-01-01

    Full Text Available Secular variations of the geomagnetic field have been measured with a continuously improving accuracy during the last few hundred years, culminating nowadays with satellite data. It is however well known that the dynamics of the magnetic field is linked to that of the velocity field in the core and any attempt to model secular variations will involve a coupled dynamical system for magnetic field and core velocity. Unfortunately, there is no direct observation of the velocity. Independently of the exact nature of the above-mentioned coupled system – some version being currently under construction – the question is debated in this paper whether good knowledge of the magnetic field can be translated into good knowledge of core dynamics. Furthermore, what will be the impact of the most recent and precise geomagnetic data on our knowledge of the geomagnetic field of the past and future? These questions are cast into the language of variational data assimilation, while the dynamical system considered in this paper consists in a set of two oversimplified one-dimensional equations for magnetic and velocity fields. This toy model retains important features inherited from the induction and Navier-Stokes equations: non-linear magnetic and momentum terms are present and its linear response to small disturbances contains Alfvén waves. It is concluded that variational data assimilation is indeed appropriate in principle, even though the velocity field remains hidden at all times; it allows us to recover the entire evolution of both fields from partial and irregularly distributed information on the magnetic field. This work constitutes a first step on the way toward the reassimilation of historical geomagnetic data and geomagnetic forecast.

  18. Smartphone-Based Indoor Pedestrian Tracking Using Geo-Magnetic Observations

    Directory of Open Access Journals (Sweden)

    Sungnam Lee

    2013-01-01

    Full Text Available With the widespread use of smartphones, the use of location-based services (LBS with smartphones has become an active research issue. The accurate measurement of user location is necessary to provide LBS. While outdoor locations are easily obtained with GPS, indoor location information is difficult to acquire. Previous work on indoor location tracking systems often relied on infrastructures that are influenced by environmental changes and temporal differences. Several studies have proposed infrastructure-less systems that are independent of the surroundings, but these works generally required non-trivial computation time or energy costs. In this paper, we propose an infrastructure-less pedestrian tracking system in indoor environments. The system uses accelerometers and magnetic sensors in smartphones without pre-installed infrastructure. We reduced the cumulative error of location tracking by geo-magnetic observations at corners and spots with magnetic fluctuations. In addition, we developed a robust estimation model that is tolerant to false positives, as well as a mobility model that reflects the characteristics of multiple sensors. Extensive evaluation in a real environment indicates that our system is accurate and cost-effective.

  19. Geomagnetism 4

    CERN Document Server

    Jacobs, John A

    2013-01-01

    Geomagnetism, Volume 4 focuses on the processes, methodologies, technologies, and approaches involved in geomagnetism, including electric fields, solar wind plasma, pulsations, and gravity waves.The selection first offers information on solar wind, magnetosphere, and the magnetopause of the Earth. Discussions focus on magnetopause structure and transfer processes, magnetosphere electric fields, geomagnetically trapped radiation, microstructure of the solar wind plasma, and hydro magnetic fluctuations and discontinuities. The text then examines geomagnetic tail, neutral upper atmosphere, and ge

  20. Quality Control of Observation Data by the Geomagnetic Network of China

    OpenAIRE

    Suqin Zhang; Changhua Fu; Yufei He; Dongmei Yang; Qi Li; Xudong Zhao; Jianjun Wang

    2016-01-01

    Data quality is an important guarantee for scientific research. The Geomagnetic Network of China (GNC) controls data quality for all observatories under the jurisdiction of China Earthquake Administration. This paper presents the quality control content and methods; quality evaluation and feedback procedures; and the process for publishing data sets via the GNC website. Technical challenges and proposed quality assurance procedures for future GNC data sets are described.

  1. A Carrington-like geomagnetic storm observed in the 21st century

    CERN Document Server

    Cid, C; Guerrero, A; Palacios, J; Cerrato, Y

    2015-01-01

    In September 1859 the Colaba observatory measured the most extreme geomagnetic disturbance ever recorded at low latitudes related to solar activity: the Carrington storm. This paper describes a geomagnetic disturbance case with a profile extraordinarily similar to the disturbance of the Carrington event at Colaba: the event on 29 October 2003 at Tihany magnetic observatory in Hungary. The analysis of the H-field at different locations during the "Carrington-like" event leads to a re-interpretation of the 1859 event. The major conclusions of the paper are the following: (a) the global Dst or SYM-H, as indices based on averaging, missed the largest geomagnetic disturbance in the 29 October 2003 event and might have missed the 1859 disturbance, since the large spike in the horizontal component (H) of terrestrial magnetic field depends strongly on magnetic local time (MLT); (b) the main cause of the large drop in H recorded at Colaba during the Carrington storm was not the ring current but field-aligned currents ...

  2. A Carrington-like geomagnetic storm observed in the 21st century

    Directory of Open Access Journals (Sweden)

    Cid Consuelo

    2015-01-01

    Full Text Available In September 1859 the Colaba observatory measured the most extreme geomagnetic disturbance ever recorded at low latitudes related to solar activity: the Carrington storm. This paper describes a geomagnetic disturbance case with a profile extraordinarily similar to the disturbance of the Carrington event at Colaba: the event on 29 October 2003 at Tihany magnetic observatory in Hungary. The analysis of the H-field at different locations during the “Carrington-like” event leads to a re-interpretation of the 1859 event. The major conclusions of the paper are the following: (a the global Dst or SYM-H, as indices based on averaging, missed the largest geomagnetic disturbance in the 29 October 2003 event and might have missed the 1859 disturbance, since the large spike in the horizontal component (H of terrestrial magnetic field depends strongly on magnetic local time (MLT; (b the main cause of the large drop in H recorded at Colaba during the Carrington storm was not the ring current but field-aligned currents (FACs; and (c the very local signatures of the H-spike imply that a Carrington-like event can occur more often than expected.

  3. Satellite and Ground-Based Observations of Auroral Energy Deposition and the Effects on Thermospheric Composition During Large Geomagnetic Storms: 1. Great Geomagnetic Storm of 20 November 2003

    Science.gov (United States)

    2008-01-01

    studies during both distribution of low-energy electrons well below 1 keV that are geomagnetically quiet and disturbed periods [e.g., see Nier the suspected...4510. energies inferred from the Sondre Stromtjord radar, J. Geophys. Res., 96, Nier , A. 0., W. E. Potter, and D. C. Kayser (1976), Atomic and

  4. Geomagnetic Storm Main Phase effect on the Equatorial Ionosphere as measured from GPS observations at Ile-Ife

    Science.gov (United States)

    Olabode, Ayomide; Ariyibi, Emmanuel

    2016-07-01

    The effect of the main phase of two intense geomagnetic storm events which occurred on August 5-6 and September 26-27, 2011 on the equatorial ionosphere have been investigated using Global Positioning System (GPS) data obtained from an Ile-Ife station (geomagnetic lat. 9.84°N, long. 77.25°E). The WinTEC-P and GPS-TEC analysis software programs were used to process the GPS data to obtain Total Electron Content (TEC) and Scintillation Index (S4). TEC profiles during the main phase of the two geomagnetically disturbed days were compared with quiet time average profiles to examine the response of the equatorial ionosphere. International Reference Ionosphere (IRI) 2012 TEC model was also obtained from Virtual Ionosphere, Thermosphere, Mesosphere Observatory (VITMO) and the extents of deviation from measured GPS-derived TEC were examined for the main phase of the storm events. The results showed that the intensity of both storm events during the main phase which occurred at night-time correlated well with a strong southward direction of the z-component of the Interplanetary Magnetic Field (IMF-Bz) and Solar Wind Speed (Vsw), with the Disturbance storm time (Dst) profile showing multiple step development. TEC depletion was observed during the main phase of the August 5-6, 2011 storm event with TEC recording a maximum value of 9.31 TECU. A maximum TEC value of 55.8 TECU was recorded during the main phase of the September 26-27, 2011 storm event depicting TEC enhancement. Significant scintillation index value of 0.57 was observed when the main phase started on August 5-6, 2011 followed by a prolonged suppression while there was less significant scintillation impact on September 26-27, 2011 with a maximum value of 0.33. The study concluded that the intensification of the ring current during the main phase of geomagnetic storm events was responsible for the intensity of the storm events causing large variations in TEC and significant scintillation phenomenon.

  5. Satellite Geomagnetism

    DEFF Research Database (Denmark)

    Olsen, Nils; Stolle, Claudia

    2012-01-01

    Observations of Earth’s magnetic field from space began more than 50 years ago. A continuous monitoring of the field using low Earth orbit (LEO) satellites, however, started only in 1999, and three satellites have taken highprecision measurements of the geomagnetic field during the past decade...... ability to characterize and understand the many sources that contribute to Earth’s magnetic field. In this review, we summarize investigations of Earth’s interior and environment that have been possible through the analysis of high-precision magnetic field observations taken by LEO satellites........ The unprecedented time-space coverage of their data opened revolutionary new possibilities for monitoring, understanding, and exploring Earth’s magnetic field. In the near future, the three-satellite constellation Swarm will ensure continuity of such measurement and provide enhanced possibilities to improve our...

  6. Thermosphere and geomagnetic response to interplanetary coronal mass ejections observed by ACE and GRACE: Statistical results

    CERN Document Server

    Krauss, S; Veronig, A M; Baur, O; Lammer, H

    2015-01-01

    For the period July 2003 to August 2010, the interplanetary coronal mass ejection (ICME) catalogue maintained by Richardson and Cane lists 106 Earth-directed events, which have been measured in-situ by plasma and field instruments onboard the ACE satellite. We present a statistical investigation of the Earth's thermospheric neutral density response by means of accelerometer measurements collected by the GRACE satellites, which are available for 104 ICMEs in the data set, and its relation to various geomagnetic indices and characteristic ICME parameters such as the impact speed, southward magnetic field strength (Bz). The majority of ICMEs causes a distinct density enhancement in the thermosphere, with up to a factor of eight compared to the pre-event level. We find high correlations between ICME Bz and thermospheric density enhancements (~0.9), while the correlation with the ICME impact speed is somewhat smaller (~0.7). The geomagnetic indices revealing the highest correlations are Dst and SYM-H (~0.9), the l...

  7. Open-source Peer-to-Peer Environment to Enable Sensor Web Architecture: Application to Geomagnetic Observations and Modeling

    Science.gov (United States)

    Holland, M.; Pulkkinen, A.

    2007-12-01

    -reported values. Remote "browsing" peers access these modeling-run results within the Environment, but also have the option to access the sensors directly. We expect that this preparatory work will benefit the LWS/Geospace program, as real-time geomagnetic observations are relevant to Sun-Earth Connection studies.

  8. Observation and analysis of geomagnetic abnormity associated with the Ms=5.7 Jiujiang-Ruichang earthquake

    Institute of Scientific and Technical Information of China (English)

    GU Zuo-wen; ZHANG Yi; YAO Tong-qi; GAO Jin-tian; LIU Xin; CHEN Bin; ZHAN Zhi-jia; GU Chun-lei

    2006-01-01

    A three-component geomagnetic survey was carried out during the period from 2002 to 2004 in China including Jiujiang-Ruichang region. Comparing the "2005.0 surface spline model of China geomagnetic field" created on the basis of the survey data with the "1970.0 surface spline model of China geomagnetic field", we can see an obvious abnormity in the geomagnetic horizontal component within a range of about 100 km around the epicenter of the Ms=5.7 Jiujiang-Ruichang earthquake occurred on November 26, 2005. After the earthquake, we carried out a repeated geomagnetic survey at 21 stations in the Jiujiang-Ruichang region and created a corresponding "2005.0 partially revised surface spline model of China geomagnetic field". By comparing the above three models, analyzing the geomagnetic horizontal component at the profile in the Jiujiang-Ruichang region and quantitatively studying the geomagnetic data of every stations around the Ms=5.7 earthquake, we have obtained the geomagnetic abnormity associated with this earthquake. Then the geomagnetic abnormity and its relation with seismic activity are discussed in this paper.

  9. STEREO and Wind observations of a fast ICME flank triggering a prolonged geomagnetic storm on 5-7 April 2010

    CERN Document Server

    Möstl, Christian; Rollett, Tanja; Farrugia, Charles J; Liu, Ying; Veronig, Astrid M; Leitner, M; Galvin, Antoinette B; Biernat, Helfried K

    2010-01-01

    On 5 April 2010 an interplanetary (IP) shock was detected by the Wind spacecraft ahead of Earth, followed by a fast (average speed 650 km/s) IP coronal mass ejection (ICME). During the subsequent moderate geomagnetic storm (minimum Dst = -72 nT, maximum Kp=8-), communication with the Galaxy 15 satellite was lost. We link images from STEREO/SECCHI to the near-Earth in situ observations and show that the ICME did not decelerate much between Sun and Earth. The ICME flank was responsible for a long storm growth phase. This type of glancing collision was for the first time directly observed with the STEREO Heliospheric Imagers. The magnetic cloud (MC) inside the ICME cannot be modeled with approaches assuming an invariant direction. These observations confirm the hypotheses that parts of ICMEs classified as (1) long-duration MCs or (2) magnetic-cloud-like (MCL) structures can be a consequence of a spacecraft trajectory through the ICME flank.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2016-09-01

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

  12. Electro-Optics/Low Observables Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Electro-Optics/Low Observables Laboratory supports graduate instruction for students enrolled in the Low Observables program. Its purpose is to introduce these...

  13. Longitudinal differences observed in the ionospheric F-region during the major geomagnetic storm of 31 March 2001

    Directory of Open Access Journals (Sweden)

    Y. Sahai

    2004-09-01

    Full Text Available A new ionospheric sounding station using a Canadian Advanced Digital Ionosonde (CADI was established for routine measurements by the "Universidade do Vale do Paraiba (UNIVAP" at São José dos Campos (23.2° S, 45.9° W, Brazil, in August 2000. A major geomagnetic storm with gradual commencement at about 01:00 UT was observed on 31 March 2001. In this paper, we present and discuss salient features from the ionospheric sounding measurements carried out at S. J. Campos on the three consecutive UT days 30 March (quiet, 31 March (disturbed and 1 April (recovery 2001. During most of the storm period, the foF2 values showed negative phase, whereas during the two storm-time peaks, large F-region height variations were observed. In order to study the longitudinal differences observed in the F-region during the storm, the simultaneous ionospheric sounding measurements carried out at S. J. Campos, El Arenosillo (37.1° N, 6.7° W, Spain, Okinawa (26.3° N, 127.8° E, Japan and Wakkanai (45.5° N, 141.7° E, Japan, during the period 30 March-1 April 2001, have been analyzed. A comparison of the observed ionospheric parameters (h'F and foF2 in the two longitudinal zones (1. Japanese and 2. Brazilian-Spanish shows both similarities and differences associated with the geomagnetic disturbances. Some latitudinal differences are also observed in the two longitudinal zones. In addition, global ionospheric TEC maps from the worldwide network of GPS receivers are presented, showing widespread TEC changes during both the main and recovery phases of the storm. The ionospheric sounding measurements are compared with the ASPEN-TIMEGCM model runs appropriate for the storm conditions. The model results produce better agreement during the quiet period. During the disturbed period, some of the observed F-region height variations are well reproduced by the model results. The model foF2 and TEC results differ considerably during the

  14. Some aspects of geomagnetically conjugate phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Rycroft, M.J.

    1987-12-01

    Both charged particles and waves convey information about the thermosphere, ionosphere and magnetosphere from the Northern to the Southern Hemisphere and vice versa, along geomagnetic flux tubes.The interhemispheric travel time of electrons or ions, being dependent upon L-value , pitch angle and energy (which may lie between less than or equal to 1 eV and greater than or equal to 1 MeV) may be many hours, ranging down to less than or equal to 1 s. However, the one-hop propagation time for magnetohydrodynamic or whistler mode waves generally lies between 10/sup 2/s and 1 s. Such times, therefore, give the time scales of transient phenomena that are geomagnetically conjugate and of changes in steady-state plasma processes occurring in geomagnetically conjugate regions. Contrasting examples are presented of conjugate physical phenomena, obtained using satellite, rocket, aircraft and ground-based observations; the latter capitalise upon the rather rare disposition of land - rather than ocean - at each end of a geophysically interesting flux tube. Particular attention is paid to the interactions between whistler mode waves and energetic electrons. Geomagnetic, radio, optical and plasma observations, taken together with model computations, provide a wealth of knowledge on conjugate phenomena and their dependence on conditions in the solar wind, substorms, L-value, etc... Finally, some suggestions are made for future lines of research.

  15. An electromagnetic sounding experiment in Germany using the vertical gradient of geomagnetic variations observed in a deep borehole

    Science.gov (United States)

    Schmucker, Ulrich; Spitzer, Klaus; Steveling, Erich

    2009-09-01

    We have recorded for 13 d, geomagnetic variations simultaneously on the Earth's surface and in a borehole at 832 m depth straight below, with a sampling rate of 1 Hz. In addition, geoelectric variations were observed at the same site near Bad Königshofen in Frankonia, Germany. The penetrated moderately conductive Triassic sediments lie above highly resistive Permian deposits. A presumably crystalline basement begins at 1500-1900 m depth. The purpose of the experiment is to determine the skin effect of geomagnetic variations and to derive from it the equivalent to the magnetotelluric (MT) surface impedance, using the vertical gradient (VG) method of electromagnetic (EM) sounding. In this way, we were able to reproduce all four elements of the MT impedance tensor, except for an unexplained but consistent downward shift of VG phases against MT phases by roughly 15° for the two off-diagonal elements. Hence, our tensor evaluation goes beyond the common practice, to express the skin effect by a single VG transfer function in response to a layered structure. The otherwise good agreement of VG and MT results implies that at our test site, the MT impedance tensor is largely distortion-free and that, for example, its pronounced anisotropy should be regarded as a genuine characteristic of the EM response for a laterally non-uniform or possibly anisotropic deep structure. The drilling site lies within the range of a widespread induction anomaly. We have observed the resulting variations of the vertical magnetic component at the surface and in the borehole and found them to be identical. The thus established absence of a skin effect for the vertical component allows us to treat the sedimentary layer down to the depth of the borehole instrument as a thin sheet, and the pertinent thin-sheet approximation for EM induction forms the basis of our analysis. We have derived the required estimate of conductance from the skin effect of horizontal components, noting that this estimate

  16. Morphology of the southern African geomagnetic field derived from observatory and repeat station survey observations: 2005-2014

    Science.gov (United States)

    Kotzé, P. B.; Korte, M.

    2016-02-01

    Geomagnetic field data from four observatories and annual field surveys between 2005 and 2015 provide a detailed description of Earth's magnetic field changes over South Africa, Namibia and Botswana on time scales of less than 1 year. The southern African area is characterized by rapid changes in the secular variation pattern and lies in close proximity to the South Atlantic Anomaly (SAA) where the geomagnetic field intensity is almost 30 % weaker than in other regions at similar latitudes around the globe. Several geomagnetic secular acceleration (SA) pulses (geomagnetic jerks) around 2007, 2010 and 2012 could be identified over the last decade in southern Africa. We present a new regional field model for declination and horizontal and vertical intensity over southern Africa (Southern African REGional (SAREG)) which is based on field survey and observatory data and covering the time interval from 2005 to 2014, i.e. including the period between 2010 and 2013 when no low Earth-orbiting vector field satellite data are available. A comparative evaluation between SAREG and global field models like CHAOS-5, the CHAMP, Orsted and SAC-C model of the Earth's magnetic field and International Geomagnetic Reference Field (IGRF-12) reveals that a simple regional field model based on a relatively dense ground network is able to provide a realistic representation of the geomagnetic field in this area. We particularly note that a global field model like CHAOS-5 does not always indicate similar short-period patterns in the field components as revealed by observatory data, while representing the general secular variation reasonably well during the time interval without near-Earth satellite vector field data. This investigation further shows the inhomogeneous occurrence and distribution of secular variation impulses in the different geomagnetic field components and at different locations in southern African.

  17. Impacts of Geomagnetic storms on the mid-latitude mesosphere and lower thermosphere observed by a Na lidar and TIMED/GUVI

    Science.gov (United States)

    Yuan, T.; Zhang, Y.

    2015-12-01

    In this paper, we report our findings on the correlation between the neutral temperature (around the mesopause) and thermospheric column density O/N2 ratio, along with their response to geomagnetic storms above mid-latitude of North America. A temperature/wind Doppler Na lidar, operating at Fort Collins, CO (41°N, 105°W) and later at Logan, UT (42°N and 112°W), observed significant temperature increases (temperature anomaly) above 95 km (as much as 55 K at 105 km altitude) during four geomagnetic storms (April 2002, Nov. 2004, May 2005 and Oct. 2012). Coincident TIMED/GUVI observations indicate significant depletion in the thermospheric O/N2 ratio at the lidar locations. These observations suggest that the local mesopause warming seen by the lidar is due to transport of the high-latitude Joule and particle heated neutrals at the E and F layers to the mid-latitude region.

  18. Significant geomagnetic differences in both phase and amplitude observed at "conjugate" polar latitudes near the December 1903 Solstice

    Science.gov (United States)

    Egeland, Alv; Deehr, Charles

    2014-05-01

    During Roald Amundsen's exploration of the Northwest Passage (1903-1906) he conducted systematic measurements of diurnal and seasonal variations of the north magnetic dip pole (NMDP) at Gjøahavn (~ 68 N, 95 E). The NMDP variations have been largely interpreted as indicating control by the polarity of the interplanetary magnetic field (IMF); the Svalgard-Mansurov (S-M) effect. In Sir Robert Scott's Discovery expedition, geomagnetic observations were made in 1903 from Cape Armitage, Antarctica (~78 S, 168 E). Unwittingly, the measurements of Amundsen and Scott were acquired near conjugate ends of the same magnetic field lines. While their separation in solar local time is ~ 5 hours, they differ in magnetic local time less than 1/2 hour. However, up to this time no direct comparison of the two sets of magnetic observations has ever been made. This presentation contains an analysis of magnetic perturbations observed at both locations for comparison with contemporary and present day monthly-averaged diurnal variations, even if the overlap in data among these expeditions is somewhat limited. The near magnetic conjugacy of Gjøahavn- Cape Armitage locations makes these measurements valuable. Our analysis shows: (1) While similar variations appeared at both ends of the joining magnetic field they manifest significant differences in both phase and amplitude, (2) present day NMDP variations appear consistent with the S-M effect analyses when compared with satellite measurements of solar wind/IMF measurements, (3) differences at the "conjugate" locations cannot be explained in terms of the S-M effect alone. The roles of lobe cell and ionospheric conductance at polar magnetically "conjugate" locations are used to explain the observed phase and amplitude differences.

  19. Radiation belt electron acceleration during the 17 March 2015 geomagnetic storm: Observations and simulations

    Science.gov (United States)

    Li, W.; Ma, Q.; Thorne, R. M.; Bortnik, J.; Zhang, X.-J.; Li, J.; Baker, D. N.; Reeves, G. D.; Spence, H. E.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Blake, J. B.; Fennell, J. F.; Kanekal, S. G.; Angelopoulos, V.; Green, J. C.; Goldstein, J.

    2016-06-01

    Various physical processes are known to cause acceleration, loss, and transport of energetic electrons in the Earth's radiation belts, but their quantitative roles in different time and space need further investigation. During the largest storm over the past decade (17 March 2015), relativistic electrons experienced fairly rapid acceleration up to ~7 MeV within 2 days after an initial substantial dropout, as observed by Van Allen Probes. In the present paper, we evaluate the relative roles of various physical processes during the recovery phase of this large storm using a 3-D diffusion simulation. By quantitatively comparing the observed and simulated electron evolution, we found that chorus plays a critical role in accelerating electrons up to several MeV near the developing peak location and produces characteristic flat-top pitch angle distributions. By only including radial diffusion, the simulation underestimates the observed electron acceleration, while radial diffusion plays an important role in redistributing electrons and potentially accelerates them to even higher energies. Moreover, plasmaspheric hiss is found to provide efficient pitch angle scattering losses for hundreds of keV electrons, while its scattering effect on > 1 MeV electrons is relatively slow. Although an additional loss process is required to fully explain the overestimated electron fluxes at multi-MeV, the combined physical processes of radial diffusion and pitch angle and energy diffusion by chorus and hiss reproduce the observed electron dynamics remarkably well, suggesting that quasi-linear diffusion theory is reasonable to evaluate radiation belt electron dynamics during this big storm.

  20. Observations at geosynchronous orbit of a persistent Pc5 geomagnetic pulsation and energetic electron flux modulations

    Directory of Open Access Journals (Sweden)

    T. E. Sarris

    2007-07-01

    Full Text Available A long lasting narrow-band (4–7 mHz Pc5 fluctuation event at geosynchronous orbit is presented through measurements from GOES-8 and GOES-10 and the response of energetic electrons with drift frequencies close to the narrow-band pulsation frequency is monitored through a spectral analysis of flux data from the LANL-SOPA energetic electron instrument. This analysis shows electron flux modulations at the magnetospheric pulsation's frequency as well as at various other frequencies in the Pc5 range, related to the particles' drift-frequencies and their harmonics. A drift resonance effect can be seen, with electron flux modulation becoming more evident in the energy channels of electrons with drift frequencies closer to the wave frequency; however no net increase or decrease in energetic electron flux is observed, indicating that the net energy transfer and transport of electrons is not significant. This Pc5 event has a long duration, being observed for more than a couple of days at geosynchronous orbit over several traversals of the two GOES satellites, and is localized in azimuthal extent. Spectral analysis shows that most of the power is in the transverse components. The frequency of the narrow-band event, as observed at geosynchronous orbit shifts during the time of the event from 7±0.5 mHz to about 4±0.5 mHz. On the ground, CARISMA magnetometers record no distinct narrow-band fluctuation in the magnetic field, and neither does Geotail, which is traversing the outer magnetosphere a few RE further out from geosynchronous orbit, at the same UT and LT that GOES-8 and -10 observe the pulsations, suggesting that that there is no connection to external fluctuations originating in the solar wind. An internal generation mechanism is suggested, such as could be provided by energetic ring current particles, even though conclusive evidence could not be provided for this particular event. Through a statistical study, it is

  1. Observations of energetic helium ions in the earth's radiation belts during a sequence of geomagnetic storms

    Science.gov (United States)

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

    1981-01-01

    Observations of energetic (MeV) helium ions made with Explorer 45 during a sequence of magnetic storms during June through December of 1972 are presented. It is noted that the first of these storms started on June 17 and had a Dst index excursion to -190 gamma and that the MeV helium ions were perturbed primarily beyond 3 earth radii in the equatorial radiation belts with a typical flux increase of an order of magnitude at L equal to 4. The second storm period was in August and was associated with very major solar flare activity. While the Dst extremum was at best 35 gamma less than the June storm, this period can be characterized as irregular (or multi-storm) with strong compression of the magnetosphere and very large (order of magnitude) MeV helium ion flux enhancements down to L approximately equal to 2. After this injection, the trapped helium ion fluxes showed positive spherical slope with the peak beyond 3.15 MeV at L equal to 2.5; at the lowest observable L shells, little flux decay was seen during the remainder of the year.

  2. Prediction of Geomagnetic Storm Strength from Inner Heliospheric In Situ Observations

    CERN Document Server

    Kubicka, M; Amerstorfer, T; Boakes, P D; Feng, L; Eastwood, J P; Tormanen, O

    2016-01-01

    Prediction of the effects of coronal mass ejections (CMEs) on Earth strongly depends on knowledge of the interplanetary magnetic field southward component, Bz. Predicting the strength and duration of Bz inside a CME with sufficient accuracy is currently impossible, which forms the so-called Bz problem. Here, we provide a proof-of-concept of a new method for predicting the CME arrival time, speed, Bz and the resulting Dst index at Earth based only on magnetic field data, measured in situ in the inner heliosphere (< 1AU). On 2012 June 12-16, three approximately Earthward-directed and interacting CMEs were observed the by the STEREO imagers, and by Venus Express (VEX) in situ at 0.72 AU, 6 degree away from the Sun Earth line. The CME kinematics are calculated using the drag-based and WSA-Enlil models, constrained by the arrival time at VEX, resulting in the CME arrival time and speed at Earth. The CME magnetic field strength is scaled with a power law from VEX to Wind. Our investigation shows promising result...

  3. Multispacecraft observations and modeling of the 22/23 June 2015 geomagnetic storm

    Science.gov (United States)

    Reiff, P. H.; Daou, A. G.; Sazykin, S. Y.; Nakamura, R.; Hairston, M. R.; Coffey, V.; Chandler, M. O.; Anderson, B. J.; Russell, C. T.; Welling, D.; Fuselier, S. A.; Genestreti, K. J.

    2016-07-01

    The magnetic storm of 22-23 June 2015 was one of the largest in the current solar cycle. We present in situ observations from the Magnetospheric Multiscale Mission (MMS) and the Van Allen Probes (VAP) in the magnetotail, field-aligned currents from AMPERE (Active Magnetosphere and Planetary Electrodynamics Response), and ionospheric flow data from Defense Meteorological Satellite Program (DMSP). Our real-time space weather alert system sent out a "red alert," correctly predicting Kp indices greater than 8. We show strong outflow of ionospheric oxygen, dipolarizations in the MMS magnetometer data, and dropouts in the particle fluxes seen by the MMS Fast Plasma Instrument suite. At ionospheric altitudes, the AMPERE data show highly variable currents exceeding 20 MA. We present numerical simulations with the Block Adaptive Tree-Solarwind - Roe - Upwind Scheme (BATS-R-US) global magnetohydrodynamic model linked with the Rice Convection Model. The model predicted the magnitude of the dipolarizations, and varying polar cap convection patterns, which were confirmed by DMSP measurements.

  4. Pc3 activity at low geomagnetic latitudes - A comparison with solar wind observations

    Science.gov (United States)

    Villante, U.; Lepidi, S.; Vellante, M.; Lazarus, A. J.; Lepping, R. P.

    1992-10-01

    On an hourly time-scale the different roles of the solar wind and interplanetary magnetic field (IMF) parameters on ground micropulsation activity can be better investigated than at longer time-scales. A long-term comparison between ground measurements made at L'Aquila and IMP 8 observations confirms the solar wind speed as the key parameter for the onset of pulsations even at low latitudes, although additional control of the energy transfer from the interplanetary medium to the earth's magnetosphere is clearly exerted by the cone angle. Above about 20 mHz the frequency of pulsations is confirmed to be closely related to the IMF magnitude while, in agreement with model predictions, the IMF magnitude is related to the amplitude of the local fundamental resonant mode. We provide an interesting example in which high resolution measurements simultaneously obtained in the foreshock region and on the ground show that external transversal fluctuations do not penetrate deep into the low latitude magnetosphere.

  5. Observed Coupling Between the International Space Station PCU Plasma and a FPMU Langmuir Probe Facilitated by the Geomagnetic Field

    Science.gov (United States)

    Hartman, William; Koontz, Steven L.

    2010-01-01

    Electrical charging of the International Space Station (ISS) is a matter of serious concern resulting from the possibility of vehicle arcing and electrical shock hazard to crew during extravehicular activity (EVA). A Plasma Contactor Unit (PCU) was developed and integrated into ISS in order to control the ISS floating potential, thereby, minimize vehicle charging and associated hazards. One of the principle factors affecting ISS electrical charging is the ionosphere plasma state (i.e., electron temperature and density). To support ISS electrical charging studies a Floating Potential Monitoring Unit (FPMU) is also integrated into ISS in order to measure the ionosphere properties using Langmuir probes (LP). The FPMU was located on the Starboard side of ISS. The PCU is located near the center of ISS with its plasma exhaust pointed to port. From its integration on ISS in 2006 through November of 2009, the FPMU data exhibited nominal characteristics during PCU operation. On November 21, 2009 the FPMU was relocated from the Starboard location to a new Port location. After relocation significant enhanced noise was observed in both the LP current-voltage sweeps and the derived electron temperature data. The enhanced noise only occurred when the PCU was in discharge and at unique and repeatable locations of the ISS orbit. The cause of this enhanced noise was investigated. It was found that there is coupling occurring between the PCU plasma and the FPMU LP. In this paper we shall 1) present the on-orbit data and the presence of enhanced noise, 2) demonstrate that the coupling of the PCU plasma and the FPMU measurements is geomagnetically organized, 3) show that coupling of the PCU plasma and the FPMU is primarily due to and driven by particle-wave interaction and 4) show that the ionosphere conditions are adequate for Alfven waves to be generated by the PCU plasma.

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

    Science.gov (United States)

    Khachikyan, Galina

    2016-07-01

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

  7. An Ensemble Algorithm Based Component for Geomagnetic Data Assimilation

    Directory of Open Access Journals (Sweden)

    Zhibin Sun and Weijia Kuang

    2015-01-01

    Full Text Available Geomagnetic data assimilation is one of the most recent developments in geomagnetic studies. It combines geodynamo model outputs and surface geomagnetic observations to provide more accurate estimates of the core dynamic state and provide accurate geomagnetic secular variation forecasting. To facilitate geomagnetic data assimilation studies, we develop a stand-alone data assimilation component for the geomagnetic community. This component is used to calculate the forecast error covariance matrices and the gain matrix from a given geodynamo solution, which can then be used for sequential geomagnetic data assimilation. This component is very flexible and can be executed independently. It can also be easily integrated with arbitrary dynamo models.

  8. An extensive survey of dayside diffuse aurora based on optical observations at Yellow River Station

    CERN Document Server

    Han, De-Sheng; Liu, Jian-Jun; Qiu, Qi; Keika, K; Hu, Ze-Jun; Liu, Jun-Ming; Hu, Hong-Qiao; Yang, Hui-Gen

    2016-01-01

    By using 7 years optical auroral observations obtained at Yellow River Station (magnetic latitude $76.24\\,^{\\circ}{\\rm C}$N) at Ny-Alesund, Svalbard, we performed the first extensive survey for the dayside diffuse auroras (DDAs) and acquired observational results as follows. (1) The DDAs can be classified into two broad categories, i.e., unstructured and structured DDAs. The unstructured DDAs are mainly distributed in the morning and afternoon, but the structured DDAs predominantly occurred around the magnetic local noon (MLN). (2) The unstructured DDAs observed in morning and afternoon present obviously different properties. The afternoon ones are much stable and seldom show pulsating property. (3) The DDAs are more easily observed under geomagnetically quiet times. (4) The structured DDAsmainly show patchy, stripy, and irregular forms and are often pulsating and drifting. The drifting directions are mostly westward (with speed $\\sim$5km/s), but there are cases showing eastward or poleward drifting. (5) The ...

  9. Impacts of CME-induced geomagnetic storms on the midlatitude mesosphere and lower thermosphere observed by a sodium lidar and TIMED/GUVI

    Science.gov (United States)

    Yuan, T.; Zhang, Y.; Cai, X.; She, C.-Y.; Paxton, L. J.

    2015-09-01

    In this paper, we report our findings on the correlation between the neutral temperature (around the mesopause) and thermospheric column density O/N2 ratio, along with their response to geomagnetic storms above midlatitude of North America. A temperature/wind Doppler Na lidar, operating at Fort Collins, CO (41°N, 105°W), and later at Logan, UT (42°N and 112°W), observed significant temperature increases (temperature anomaly) above 95 km (as much as 55 K at 105 km altitude) during four coronal mass ejection-induced geomagnetic storms (April 2002, November 2004, May 2005, and October 2012). Coincident Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Global Ultraviolet Spectrographic Imager observations indicate significant depletion in the thermospheric O/N2 ratio at the lidar locations. These observations suggest that the local mesopause warming seen by the lidar is due to transport of the high-latitude joule and particle heated neutrals at the E and F layers to the midlatitude region.

  10. Optical Observations Of Fermi LAT Monitored Blazars

    Science.gov (United States)

    Cook, Kyle; Carini, M. T.

    2009-01-01

    For the past 8 years the Bell Observatory at Western Kentucky University has been conducting R band monitoring of the variability of approximately 50 Blazars. A subset of these objects are being routinely observed with the LAT instrument on-board the Fermi Space Telescope. Adding the Robotically Controlled Telescope (RCT) at Kitt Peak National Observatory and observations with the AZT-11 telescope at the Crimean Astrophysical Observatory (CRAO), we are intensively monitoring the Blazars on the Lat monitoring list. We present the results of our long term monitoring of the LAT monitored Blazars, as well as the recent contemporaneous optical R band observations we have obtained of the LAT Blazars.

  11. Simultaneous observations of the near-earth and distant geomagnetic tail during a substorm by ISEE-1, ISEE-3 and geostationary spacecraft

    Science.gov (United States)

    Richardson, I. G.; Scholer, M.; Tsurutani, B. T.; Daly, P. W.; Baker, D. N.

    1987-01-01

    The structure of the geomagnetic tail during a substorm is investigated by combining plasma, magnetic field, and energetic particle data from the ISEE-3 spacecraft in the deep tail with similar near-earth observations from ISEE-1 and geostationary spacecraft. The observations can be interpreted in terms of the neutral-line model of substorms and indicate the formation of a closed-loop field region (plasmoid) following substorm onset, which is ejected down the tail. The plasmoid is observed to have a double-loop field strucure. This may be the result of a second substorm onset occurring about 25 min after the first, producing a further near-earth neutral line and closed field loop. During the substorm recovery phase, the substorm neutral line moves tailward to beyond 130 earth radii from earth by some 3 h after substorm onset.

  12. Experimental observation of optical Weyl points

    CERN Document Server

    Noh, Jiho; Leykam, Daniel; Chong, Y D; Chen, Kevin; Rechtsman, Mikael C

    2016-01-01

    Weyl fermions are hypothetical two-component massless relativistic particles in three-dimensional (3D) space, proposed by Hermann Weyl in 1929. Their band-crossing points, called 'Weyl points,' carry a topological charge and are therefore highly robust. There has been much excitement over recent observations of Weyl points in microwave photonic crystals and the semimetal TaAs. Here, we report on the first experimental observation of Weyl points of light at optical frequencies. These are also the first observations of 'type-II' Weyl points for photons, which have strictly positive group velocity along one spatial direction. We use a 3D structure consisting of laser-written waveguides, and show the presence of type-II Weyl points by (1) observing conical diffraction along one axis when the frequency is tuned to the Weyl point; and (2) observing the associated Fermi arc surface states. The realization of Weyl points at optical frequencies allow these novel electromagnetic modes to be further explored in the cont...

  13. Geomagnetic Principal Magnetic Storms

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The abbreviations used for observatory names are as follows: GEOMAGNETIC OBSERVATORIES Code Station Geomagnetic Latitude ABG Alibag AMS Martin de Vivie. These data...

  14. Nighttime mesospheric hydroxyl enhancements during SEP events and accompanying geomagnetic storms: Ionization rate modeling and Aura satellite observations

    Science.gov (United States)

    Verkhoglyadova, O. P.; Wissing, J. M.; Wang, S.; Kallenrode, M.-B.; Zank, G. P.

    2016-07-01

    We quantify the effects of combined precipitating solar protons and magnetospheric electrons on nighttime odd hydrogen density enhancements during two solar energetic particle (SEP) events accompanied by strong geomagnetic storms. We perform detailed modeling of ionization rates for 7-17 November 2004 and 20-30 August 2005 intervals with improved version 1.6 of the Atmospheric Ionization Module Osnabrück model. Particle measurements from Geostationary Operational Environmental Satellites and Polar Orbiting Environmental Satellites are sorted and combined in 2 h intervals to create realistic particle precipitation maps that are used as the modeling input. We show that modeled atmospheric ionization rates and estimated peak odd hydrogen (primarily hydroxyl) production from 0.001 hPa to 0.1 hPa atmospheric pressure levels during these intervals are consistent with enhancements in nighttime averaged zonal odd hydrogen densities derived from newly reprocessed and improved data set of Microwave Limb Sounder instrument on board Aura satellite. We show that both precipitating SEPs and magnetospheric electrons contribute to mesospheric ionization and their relative contributions change throughout the intervals. Our event-based modeling results underline the importance of the combined ionization sources for odd hydrogen chemistry in the middle atmosphere.

  15. Multi-Instrument Observations of a Geomagnetic Storm and its Effects on the Arctic Ionosphere: A Case Study of the 19 February 2014 Storm

    DEFF Research Database (Denmark)

    Durgonics, Tibor; Komjathy, Attila; Verkhoglyadova, Olga;

    2017-01-01

    We present a multi-instrumented approach for the analysis of the Arctic ionosphere during the 19 February 2014 highly complex, multiphase geomagnetic storm, which had the largest impact on the disturbance storm-time (Dst) index that year. The geomagnetic storm was the result of two powerful Earth...

  16. Swift and optical observations of GRB 050401

    CERN Document Server

    De Pasquale, M; Barthelmy, S D; Boyd, P; Burrows, D N; Fink, R; Geherls, N; Kobayashi, S; Mason, K O; McNought, R; Nousek, J A; Page, K L; Palmer, D M; Peterson, B A; Price, P A; Rich, J; Roming, P; Rosen, S R; Sakamoto, T; Schimdt, B P; Tüller, J; Wells, A A; Zane, S; Zhang, B; Ziaeepour, H; Pasquale, Massimiliano De; Beardmore, Andy P.

    2006-01-01

    We present the results of the analysis of gamma-ray and X-ray data of GRB 050401 taken with the Swift satellite, together with a series of ground-based follow-up observations. The Swift X-ray light curve shows a clear break at about 4900 seconds after the GRB. The decay indices before and after the break are consistent with a scenario of continuous injection of radiation from the 'central engine' of the GRB to the fireball. Alternatively, this behaviour could result if ejecta are released with a range of Lorentz factors with the slower shells catching up the faster at the afterglow shock position. The two scenarios are observationally indistinguishable. The GRB 050401 afterglow is quite bright in the X-ray band but weak in the optical, with an optical to X-ray flux ratio similar to those of 'dark bursts'. We detect a significant amount of absorption in the X-ray spectrum, with N_H = (1.7 +/- 0.2) x 10^22 cm^-2 at a redshift of z=2.9, which is typical of a dense circumbust medium. Such high column density impl...

  17. Geomagnetic Information Model for the Year 2013

    Directory of Open Access Journals (Sweden)

    Mario Brkić

    2012-12-01

    Full Text Available The finalization of the survey of the Basic Geomagnetic Network of the Republic of Croatia (BGNRC and completion of geomagnetic information models for the Institute for Research and Development of Defence Systems of the Ministry of Defence and the State Geodetic Administration (e.g. Brkić M., E. Jungwirth, D. Matika and Ž. Bačić, 2012, Geomagnetic Information and Safety, 3rd Conference of Croatian National Platform for Disaster Risk Reduction, National Protection and Rescue Directorate, Zagreb was followed in 2012 with validity confirmation of the GI2012 predictive model by geomagnetic observations in quiet conditions. The differences between the measured and modelled declination were found to be within the expected errors of the model. It needs to be pointed out that this was the first successful implementation of night surveying (especially suitable for geomagnetic surveys of airports in the Republic of Croatia.

  18. Incorporation of geomagnetic data and services into EPOS infrastructure

    Science.gov (United States)

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

    2016-04-01

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

  19. International Geomagnetic Reference Field

    DEFF Research Database (Denmark)

    Finlay, Chris; Maus, S.; Beggan, C. D.

    2010-01-01

    The eleventh generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2009 by the International Association of Geomagnetism and Aeronomy Working Group V‐MOD. It updates the previous IGRF generation with a definitive main field model for epoch 2005.0, a main field...

  20. Development and Application of a Synchronous Control System to Seismo-geomagnetic Field Observations%地震地磁场野外观测同步控制系统研制与应用

    Institute of Scientific and Technical Information of China (English)

    闫计明; 王新胜; 杨世英

    2015-01-01

    The application of geomagnetic measurements is mainly focused in two areas.The first is scientific re-search,national defense,and national economic and social development,such as mineral exploration.The second is to serve earthquake monitoring and prediction.Seismo-geomagnetic field measurements are regularly repeated measure-ments at several points in the field using a high-precision magnetometer.The purpose behind taking such measure-ments is to research the temporal change and spatial distribution of the local geomagnetic field before and after earthquakes.In the field,a survey grid or line is used for obtaining geomagnetic observations,the spatial coverage of which is generally not less than 1 50 km×1 50 km for a survey grid and not less than 200 km for a survey line.In ad-dition,the distance between measuring points is usually 5 ~40 km.For the measurement of total local geomagnetic intensity using mobile observations,two survey pegs (main and vice)were installed at field observation points.These observations were synchronized with a station that records the diurnal geomagnetic variation using a specialized in-strument installed under the same conditions as for high-precision magnetic measurements.The purpose of this was to reduce or eliminate short-period and diurnal variations (Sq )of the geomagnetic field.After the Xingtai Earthquake (1 966),mobile seismo-geomagnetic observations were initiated.Different from global geomagnetic measurements,the observation stations were generally set in earthquake regions or around active faults.Moreover,the repeated period of measurement was relatively short,i.e.,usually four times per year.However,irrespective of the form of measure-ment,a manual method for synchronizing the observations from the measuring stations in the field with the diurnal stations is necessary.Single independent magnetometers in the field cannot transmit data from the diurnal stations to the scene of the field observations in real time

  1. Geomagnetically Induced Currents: Principles

    Science.gov (United States)

    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.

  2. Low-latitude ionosphere response to super geomagnetic storm of 17/18 March 2015: Results from a chain of ground-based observations over Indian sector

    Science.gov (United States)

    Ramsingh; Sripathi, S.; Sreekumar, Sreeba; Banola, S.; Emperumal, K.; Tiwari, P.; Kumar, Burudu Suneel

    2015-12-01

    In this paper, we present unique results of equatorial and low-latitude ionosphere response to one of the major geomagnetic storms of the current solar cycle that occurred during 17-18 March 2015, where Dst reached its minimum of -228 nT. Here we utilized data from magnetometers, chain of ionosondes located at Tirunelveli (8.73°N, 77.70°E; geometry: 0.32°N), Hyderabad (17.36°N, 78.47°E; geometry 8.76°N), and Allahabad (25.45°N, 81.85°E; geometry 16.5°N) along with multistation GPS receivers over Indian sector. The observations showed a remarkable increase of h'F to as high as ~560 km over Tirunelveli (magnetic equator) with vertical drift of ~70 m/s at 13:30 UT due to direct penetration of storm time eastward electric fields which exactly coincided with the local time of pre-reversal enhancement (PRE) and caused intense equatorial spread F irregularities in ionosondes and scintillations in GPS receivers at wide latitudes. Plasma irregularities are so intense that their signatures are seen in Allahabad/Lucknow. Storm time thermospheric meridional winds as estimated using two ionosondes suggest the equatorward surge of gravity waves with period of ~2 h. Suppression of anomaly crest on the subsequent day of the storm suggests the complex role of disturbance dynamo electric fields and disturbance wind effects. Our results also show an interesting feature of traveling ionospheric disturbances possibly associated with disturbance meridional wind surge during recovery phase. In addition, noteworthy observations are nighttime westward zonal drifts and PRE-related total electron content enhancements at anomaly crests during main phase and counter electrojet signatures during recovery phase.

  3. Response of equatorial and low latitude ionosphere to 2015 St. Patrick's Day super geomagnetic storm: Results from a chain of ground based observations over Indian region

    Science.gov (United States)

    Samireddipalle, Sripathi; Singh, Ram; Sreekumar, Sreeba; Suneel Kumar, Buduru

    2016-07-01

    In this paper, we present unique results of equatorial and low latitude ionosphere response to one of the major geomagnetic storms of the current solar cycle that occurred during 17-18 March 2015 where Dst reached its minimum of -228 nT. Here we utilized data from magnetometers, chain of ionosondes located at Tirunelveli (8.73°N, 77.70°E; geom: 0.320N), Hyderabad (17.360N, 78.470E; geom: 8.760N) and Allahabad (25.45°N, 81.85°E; geom: 16.50N) along with multi station GPS receivers over Indian sector. The observations showed a remarkable increase of h'F to as high as ~560 km over Tirunelveli (magnetic equator) with vertical drift of ~70 m/s at 13:30 UT due to direct penetration of storm time eastward electric fields which exactly coincided with the local time of Pre-Reversal Enhancement (PRE) and caused intense ESF irregularities in ionosondes and scintillations in GPS receivers at wide latitudes. Plasma irregularities are so intense that their signatures are seen in Allahabad/Lucknow. Stormtime thermospheric meridional winds as estimated using two ionosondes suggest the equatorward surge of gravity waves with period of ~2 hrs. Suppression of anomaly crest on the subsequent day of the storm suggests the complex role of disturbance dynamo electric fields and disturbance wind effects. Our results also show an interesting feature of Traveling Ionospheric Disturbances (TIDs) possibly associated with disturbance meridional wind surge during recovery phase. In addition, noteworthy observations are nighttime westward zonal drifts and PRE related TEC enhancements at anomaly crests during main phase and CEJ signatures during recovery phase.

  4. GRBs Optical follow-up observation at Lulin observatory, Taiwan

    CERN Document Server

    Huang, K Y; Ip, W H; Tamagawa, T; Onda, K; Makishima, K

    2005-01-01

    The Lulin GRB program, using the Lulin One-meter Telescope (LOT) in Taiwan started in July 2003. Its scientific aims are to discover optical counterparts of XRFs and short and long GRBs, then to quickly observe them in multiple bands. Thirteen follow-up observations were provided by LOT between July 2003 and Feb. 2005. One host galaxy was found at GRB 031203. Two optical afterglows were detected for GRB 040924 and GRB 041006. In addition, the optical observations of GRB 031203 and a discussion of the non-detection of the optical afterglow of GRB 031203 are also reported in this article.

  5. PFISR observation of intense ion upflow fluxes associated with an SED during the 1 June 2013 geomagnetic storm

    Science.gov (United States)

    Zou, Shasha; Ridley, Aaron; Jia, Xianzhe; Boyd, Emma; Nicolls, Michael; Coster, Anthea; Thomas, Evan; Ruohoniemi, J. M.

    2017-02-01

    The Earth's ionosphere plays an important role in supplying plasma into the magnetosphere through ion upflow/outflow, particularly during periods of strong solar wind driving. An intense ion upflow flux event during the 1 June 2013 storm has been studied using observations from multiple instruments. When the open-closed field line boundary (OCB) moved into the Poker Flat incoherent scatter radar (PFISR) field of view, divergent ion fluxes were observed by PFISR with intense upflow fluxes reaching 1.9 × 1014 m-2 s-1 at 600 km altitude. Both ion and electron temperatures increased significantly within the ion upflow, and thus, this event has been classified as a type 2 upflow. We discuss factors contributing to the high electron density and intense ion upflow fluxes, including plasma temperature effect and preconditioning by storm-enhanced density (SED). Our analysis shows that the significantly enhanced electron temperature due to soft electron precipitation in the cusp can reduce the dissociative recombination rate of molecular ions above 400 km and contributed to the density increase. In addition, this intense ion upflow flux event is preconditioned by the lifted F region ionosphere due to northwestward convection flows in the SED plume. During this event, the OCB and cusp were detected by DMSP between 15 and 16 magnetic local times, unusually duskward. Results from a global magnetohydrodynamics simulation using the Space Weather Modeling Framework have been used to provide a global context for this event. This case study provides a more comprehensive mechanism for the generation of intense ion upflow fluxes observed in association with SEDs.

  6. Seasonal and diurnal variation of ELF emission occurrences at 750-Hz band observed at geomagnetically conjugate stations

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Hiroyuki (Yamagata Univ. (Japan)); Sato, Natsuo (National Inst. of Polar Research, Tokyo (Japan))

    1987-06-01

    Statistical characteristics of emission occurrence are examined, using digital data of 750-Hz intensity records obtained at the conuugate pai of statins, Syowa Station in Antarrctica and Husafell in Iceland. The geographic local time at Syowa and Husafell is magnetic local time plus 3 hours and minur 1 hour, respectively. The following notable diurnal variations and seasonal variations were found: (1) The emissions were mostly observed during the daytime in the conjugate region. However, the magnetic local time when the emission occurrence rate reached maximum at Husafell was 2-3 hours later than that at Syowa. (2) The seasonal variations of emission occurrence showed the same tendency at the conjugate stations. The emission intensities showed a maximum during local summer and a minimum during local winter in both hemispheres. The ratio fo average emission intensity in each season to the intensity in winter is approximately 2.1-2.2 for summer, 1.7-1.9 for autumn, and 1.7 for spring. From these statistical characteristics, ELF emission intensity strongly depends on not only magnetic local time but also geographic local time and seasons, suggesting that ELF emissions observed on the ground are strongly controlled by the sunlight effects. The sunlight may affect the asymmetry of wave duct enhancement and wave propagation from the magnetosphere to the ionosphere in both hemisphers. Other effects are also discussed in this paper.

  7. Observations of a gradual transition between Ps 6 activity with auroral torches and surgelike pulsations during strong geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Steen, A.; Collis, P.N.; Evans, D.; Kremser, G.; Capelle, S.; Rees, D.; Tsurutani, B.T.

    1988-08-01

    A long-lasting large-amplitude pulsation event was observed on January 10, 1983, 0200--0600 UT (0411--0745 MLT) in the ionosphere and in the magnetosphere. In the ionosphere the characteristics of the pulsations changed from being Ps 6/auroral torches toward substorms and back to Ps 6 over the 4-hour period. At the geostationary orbit (6.6 Re) the corresponding characteristics were a modulation of the high-energy (greater than or equal to20 keV) particle intensity and plasma dropouts. Following the work by Rostoker and Samson (1984), we propose an interpretation of the event in which the pulsations are caused by the Kelvin-Helmholtz instability, during an interval of strong magnetospheric convection. The gradual transition between Ps 6 pulsations and substorm structures is interpreted as being different results of the Kelvin-Helmholtz instability, caused by different states of the magnetospheric convection. The proposed explanation forms the basis for a discussion on a simplified scheme of the substorm sequence. copyright American Geophysical Union 1988

  8. Geomagnetic Indices Bulletin (GIB)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Geomagnetic Indices Bulletin is a one page sheet containing the magnetic indices Kp, Ap, Cp, An, As, Am and the provisional aa indices. The bulletin is published...

  9. Geomagnetic aa Indices

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The geomagnetic aa indices are the continuation of the series beginning in the year 1868. A full description of these indices is given in the International...

  10. Geomagnetic Storm Sudden Commencements

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Storm Sudden Commencements (ssc) 1868 to present: STORM1 and STORM2 Lists: (Some text here is taken from the International Association of Geomagnetism and Aeronomy...

  11. The latitudinal distribution of the baseline geomagnetic field during the March 17, 2015 geomagnetic storm

    Science.gov (United States)

    Alberti, Tommaso; Piersanti, Mirko; Lepreti, Fabio; Vecchio, Antonio; De Michelis, Paola; Villante, Umberto; Carbone, Vincenzo

    2016-04-01

    Geomagnetic storms (GS) are global geomagnetic disturbances that result from the interaction between magnetized plasma that propagates from the Sun and plasma and magnetic fields in the near-Earth space plasma environment. The Dst (Disturbance Storm Time) global Ring Current index is still taken to be the definitive representation for geomagnetic storm and is used widely by researcher. Recent in situ measurements by satellites passing through the ring-current region (i.e. Van Allen probes) and computations with magnetospheric field models showed that there are many other field contributions on the geomagnetic storming time variations at middle and low latitudes. Appling the Empirical Mode Decomposition [Huang et al., 1998] to magnetospheric and ground observations, we detect the different magnetic field contributions during a GS and introduce the concepts of modulated baseline and fluctuations of the geomagnetic field. In this work, we apply this method to study the latitudinal distribution of the baseline geomagnetic field during the St. Patrick's Day Geomagnetic Storm 2015 in order to detect physical informations concerning the differences between high-latitude and equatorial ground measurements.

  12. Optical Observing Conditions at Delingha Station

    Science.gov (United States)

    Tian, J. F.; Deng, L. C.; Zhang, X. B.; Lu, X. M.; Sun, J. J.; Liu, Q. L.; Zhou, Q.; Yan, Z. Z.; Xin, Y.; Wang, K.; Jiang, X. J.; Luo, Z. Q.; Yang, J.

    2016-10-01

    SONG is a global ground-based network of 1m telescopes for stellar time-domain science, an international collaboration involving many countries across the world. In order to enable a favorable duty cycle, the SONG network plans to create a homogeneous distribution of four nodes in each of the northern and southern hemispheres. An expected possibility was building one of the northern nodes in East Asia, preferably on the Qinghai-Tibetan Plateau. During the last decade, a great deal of effort has been invested in searching for a high-quality site for ground-based astronomy in China, since this has been one of the major concerns for the development of Chinese astronomy. A number of sites on the plateau have been in operation for many years, but most of them are used only for radio astronomy, as well as small optical telescopes that are used for applied astronomy. Several potential sites for large optical instruments have been identified by the plateau site survey, but so far none of them have been adequately quantitatively characterized. Here we present results from a detailed multi-year study of the Delingha site, which was eventually selected for the SONG-China node. We also describe the site-monitoring system that will allow an isolated SONG and 50BiN node to operate safely in an automated mode.

  13. Optical Observing Conditions at Delingha Station

    CERN Document Server

    Tian, J F; Zhang, X B; Lu, X M; Sun, J J; Liu, Q L; Zhou, Q; Yan, Z Z; Xin, Y; Wang, K; Jiang, X J; Luo, Z Q; Yang, J

    2016-01-01

    SONG is a global ground based network of 1 meter telescopes for stellar time-domain science, an international collaboration involving many countries across the world. In order to enable a favourable duty cycle, the SONG network plans to create a homogeneous distribution of 4 nodes in each of the northern and southern hemispheres. A natural possibility was building one of the northern nodes in East Asia, preferably on the Qinghai-Tibetan Plateau. During the last decade, a great deal of effort has been invested in searching for high a quality site for ground based astronomy in China, since this has been one of the major concerns for the development of Chinese astronomy. A number of sites on the plateau have been in operation for many years, but most of them are used only for radio astronomy, as well as small optical telescopes for applied astronomy. Several potential sites for large optical instruments have been identified by the plateau site survey, but as yet none of them have been adequately quantitatively c...

  14. Unusual optical observations of OI greenline during a geospace event on 1 February 2008

    Science.gov (United States)

    Narayanan, V. Lakshmi; Gurubaran, S.; Emperumal, K.; Patil, P. T.

    2011-09-01

    We herein report the first observations of an unusual phenomenon recorded by an all-sky airglow imager from the low-latitude site Panhala (16.8°N, 74.1°E, geographic; 8.2°N geomagnetic), on the night of 1 February 2008, during the main phase of a moderate geomagnetic storm. The observations of OI 557.7 nm emission reveal discrete, transient, filamentary structures referred to as “streaks.” No such features were seen in the OI 630.0 nm emission and the mesospheric sodium and hydroxyl emissions. Here we speculate on possible mechanisms for generation of such structures, though we cannot conclude firmly that any one of them was responsible for the observed features. This is a puzzling observation made from very low geomagnetic latitude during the main phase of a moderate recurrent geomagnetic storm in the declining phase of solar cycle. In spite of the limitations in identifying the mechanism or mechanisms responsible for this striking observation, it is felt that understanding of processes driving such unusual and rare events will substantiate our knowledge on the mysterious coupling processes occurring in the equatorial upper atmosphere.

  15. Mathematical Properties Relevant to Geomagnetic Field Modeling

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils

    2010-01-01

    properties of those spatial mathematical representations are also discussed, especially in view of providing a formal justification for the fact that geomagnetic field models can indeed be constructed from ground-based and satellite-born observations, provided those reasonably approximate the ideal......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations.The set of numerical coefficients defining this linear combination is then what one refers...... be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focussed. Time can be dealt with as an independent variable and is not explicitly considered...

  16. Mathematical Properties Relevant to Geomagnetic Field Modeling

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Hulot, Gauthier; Olsen, Nils

    2014-01-01

    properties of those spatial mathematical representations are also discussed, especially in view of providing a formal justification for the fact that geomagnetic field models can indeed be constructed from ground-based and satellite-born observations, provided those reasonably approximate the ideal situation......Geomagnetic field modeling consists in converting large numbers of magnetic observations into a linear combination of elementary mathematical functions that best describes those observations. The set of numerical coefficients defining this linear combination is then what one refers...... be directly measured. In this chapter, the mathematical foundation of global (as opposed to regional) geomagnetic field modeling is reviewed, and the spatial modeling of the field in spherical coordinates is focused. Time can be dealt with as an independent variable and is not explicitly considered...

  17. Observation of Three Mode Parametric Interactions in Long Optical Cavities

    CERN Document Server

    Zhao, C; Fan, Y; Slagmolen, S Gras B J J; Miao, H; Blair, P Barriga D G; Hosken, D J; Brooks, A F; Veitch, P J; Mudge, D; Munch, J

    2008-01-01

    We report the first observation of three-mode opto-acoustic parametric interactions of the type predicted to cause parametric instabilities in an 80 m long, high optical power cavity that uses suspended sapphire mirrors. Resonant interaction occurs between two distinct optical modes and an acoustic mode of one mirror when the difference in frequency between the two optical cavity modes is close to the frequency of the acoustic mode. Experimental results validate the theory of parametric instability in high power optical cavities.

  18. Coronal mass ejections and geomagnetic storms: Seasonal variations

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, J.L.; Gosling, J.T.; McComas, D.J.

    1992-07-01

    The well-established semiannual geomagnetic cycle, with peak activity near the equinoxes, has been attributed to the angle between the solar rotation axis and the geomagnetic dipole, which modulates the GSM Bz component in the interplanetary magnetic field (MF). This effect is predicted to be accentuated in the shocked plasma ahead of fast coronal mass ejections (CMESs); its relevance to the internal fields of the ejecta is unclear. CMEs, particularly fast events driving interplanetary shocks, are the cause of almost all large geomagnetic storms near solar maximum. We use a set of CMEs identified by ISEE-3 observations of bidirectional electron streaming, plus IMF and geomagnetic data, to investigate the semiannual geomagnetic variation and its relation to CMEs. We find that the geomagnetic effectiveness of CMEs and post-shock solar wind is well-ordered by speed and by the southward component of the IMF in GSM coordinates, as well as by preexisting geomagnetic conditions. The post-shock seasonal effect, with geomagnetic effectiveness maximizing near April 5 for negative GSEQ By and near October 5 for positive GSEQ By, is identifiable in shock and shock/CME events, but not for CME events without leading shocks. When used to complement the more fundamental causal parameter of CME speed, the seasonal effect appears to have value for prediction of geomagnetic storms.

  19. Coronal mass ejections and geomagnetic storms: Seasonal variations

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, J.L.; Gosling, J.T.; McComas, D.J.

    1992-01-01

    The well-established semiannual geomagnetic cycle, with peak activity near the equinoxes, has been attributed to the angle between the solar rotation axis and the geomagnetic dipole, which modulates the GSM Bz component in the interplanetary magnetic field (MF). This effect is predicted to be accentuated in the shocked plasma ahead of fast coronal mass ejections (CMESs); its relevance to the internal fields of the ejecta is unclear. CMEs, particularly fast events driving interplanetary shocks, are the cause of almost all large geomagnetic storms near solar maximum. We use a set of CMEs identified by ISEE-3 observations of bidirectional electron streaming, plus IMF and geomagnetic data, to investigate the semiannual geomagnetic variation and its relation to CMEs. We find that the geomagnetic effectiveness of CMEs and post-shock solar wind is well-ordered by speed and by the southward component of the IMF in GSM coordinates, as well as by preexisting geomagnetic conditions. The post-shock seasonal effect, with geomagnetic effectiveness maximizing near April 5 for negative GSEQ By and near October 5 for positive GSEQ By, is identifiable in shock and shock/CME events, but not for CME events without leading shocks. When used to complement the more fundamental causal parameter of CME speed, the seasonal effect appears to have value for prediction of geomagnetic storms.

  20. A Low Noise Fluxgate Magnetometer for Geomagnetic Relative Observation%地磁相对记录用低噪声磁通门磁力仪

    Institute of Scientific and Technical Information of China (English)

    王晓美; 滕云田; 王晨; 范晓勇; 马洁美

    2011-01-01

    With the requirements of high resolution, low noise and long-term stability characteristics for geomagnetic relative observation instrument, suppressing the influence of outside temperature on the sensor output and obtaining low temperature coefficient, the core as magnetic sensitive element of developed fluxgate sensor is formed by alloy frame of high plasticity, endurance strength wrapped with high permeability permalloy strip and excitation coil, and fiber reinforced plastics frame wrapped with pick-up and compensation coil respectively. Due to alternating amplification and deep feed-back loop,the stability and linearity of the magnetometer are promoted. Using D/A converter circuit,it implements automatic compensation for natural magnetic field. Through performance testing in magnetic field free space and comparison measuring in observatory, the noise parameter of the magnetometer is 0. 1 nT p-p (peak-peak value) ,and the temperature coefficient of 0.l'/t and H,Z components are less than 1 nT/ t.%针对地磁相对记录要求观测仪器具有高分辨力、低噪声和长期稳定性的特点,抑制外界温度对传感器输出的影响,获得较低的温度系数,研制的磁通门传感器采用高导磁率坡莫合金作为磁芯材料,激励线圈直接缠绕在高塑性、较高持久蠕变强度的环形合金骨架上,感应线圈和补偿线圈缠绕在低温度系数的玻璃钢骨架上.采用交变模拟信号处理电路、深度负反馈网络提升仪器的稳定性和线性度;采用D/A转换电路实现仪器对外界自然磁场的自动补偿.通过在零磁空间的性能测试和在观测台站的对比观测,研制的磁力仪噪声指标为峰峰值p-p 0.1 nT、温度系数D分量小于0.1′/℃、H、Z分量小于1 nT/℃.

  1. Geomagnetic Workshop, Canberra

    Science.gov (United States)

    Barton, C. E.; Lilley, F. E. M.; Milligan, P. R.

    On May 14-15, 1985, 63 discerning geomagnetists flocked to Canberra to attend the Geomagnetic Workshop coorganized by the Australian Bureau of Mineral Resources (BMR) and the Research School of Earth Sciences, Australian National University (ANU). With an aurorally glowing cast that included an International Association of Geomagnetism and Aeronomy (IAGA) president, former president, and division chairman, the Oriental Magneto-Banquet (which was the center of the meeting), was assured of success. As a cunning ploy to mask the true nature of this gastronomic extravagance from the probings of income tax departments, a presentation of scientific papers on Australian geomagnetism in its global setting was arranged.The Australian region, including New Zealand, Papua New Guinea, Indonesia, and a large sector of the Antarctic, covers one eighth of the Earth's surface and historically has played an important role in the study of geomagnetism. The region contains both the south magnetic and geomagnetic poles, and two Australian Antarctic stations (Casey and Davis) are situated in the region of the south polar cusp (see Figure 1).

  2. Magnetic rotation imaging method to measure the geomagnetic field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A new imaging method for measuring the geomagnetic field based on the magnetic rotation effect is put forward. With the help of polarization property of the sunlight reflected from the ground and the magnetic rotation of the atmosphere, the geomagnetic field can be measured by an optical system installed on a satellite. According to its principle, the three-dimensional image of the geomagnetic field can be obtained. The measuring speed of this method is very high, and there is no blind spot and distortion. In this paper, the principle of this method is presented, and some key problems are discussed.

  3. Principles of major geomagnetic storms forecasting

    Science.gov (United States)

    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).

  4. Optical SETI Observations of the Anomalous Star KIC 8462852

    CERN Document Server

    Schuetz, Marlin; Shostak, Seth; Richards, Jon

    2015-01-01

    To explore the hypothesis that KIC 8462852's aperiodic dimming is caused by artificial megastructures in orbit (Wright et al. 2015), rather than a natural cause such as cometary fragments in a highly elliptical orbit (Marengo et al. 2015), we searched for electromagnetic signals from KIC 8462852 indicative of extraterrestrial intelligence. The primary observations were in the visible optical regime using the Boquete Optical SETI Observatory in Panama. In addition, as a preparatory exercise for the possible future detection of a candidate signal (Heidmann 1991), three of six observing runs simultaneously searched radio frequencies at the Allen Telescope Array in California. No periodic optical signals greater than 67 photons/m2 within a time frame of 25 ns were seen. This limit corresponds to isotropic optical pulses of 8E22 joules. If, however, any inhabitants of KIC 8462852 were targeting our solar system (Shostak & Villard 2004), the required energy would be reduced greatly. The limits on narrowband rad...

  5. Radio and Optical Observations of DG Tau B

    CERN Document Server

    Rodríguez, Luis F; Loinard, Laurent; Zapata, Luis A; Raga, Alejandro C; Cantó, Jorge; Riera, Angels

    2012-01-01

    DG Tau B is a Class I young stellar source that drives the asymmetric HH 159 bipolar jet. At optical wavelengths it is obscured by circumstellar optically-thick material. Using VLA and JVLA observations, we determine for the first time the proper motions of this source and find them to be consistent, within error, with those of the nearby young star DG Tau. We also discuss an ejection event that is evident in the 1994 VLA data. As the optical and molecular outflows, this ejection traced in the radio continuum is markedly asymmetric and was detected only to the NW of the star. We propose that this knot, no longer detectable in the radio, could be observed in future optical images of DG Tau B. The positions of the VLA source and of a nearby infrared object are not coincident and we suggest that the VLA source traces the exciting object, while the infrared source could be a reflection lobe.

  6. Ground-based optical observation system for LEO objects

    Science.gov (United States)

    Yanagisawa, T.; Kurosaki, H.; Oda, H.; Tagawa, M.

    2015-08-01

    We propose a ground-based optical observation system for monitoring LEO objects, which uses numerous optical sensors to cover a vast region of the sky. Its potential in terms of detection and orbital determination were examined. About 30 cm LEO objects at 1000 km altitude are detectable using an 18 cm telescope, a CCD camera and the analysis software developed. Simulations and a test observation showed that two longitudinally separate observation sites with arrays of optical sensors can identify the same objects from numerous data sets and determine their orbits precisely. The proposed system may complement or replace the current radar observation system for monitoring LEO objects, like space-situation awareness, in the near future.

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

    Science.gov (United States)

    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.

  8. GRB Prompt Optical Observations by Master and Lomonosov

    Science.gov (United States)

    Gorbovskoy, Evgeny

    We present the results of the prompt, early and afterglow optical observations of five γ-ray bursts (GRBs): GRB 100901A, GRB 100902A, GRB 100905A, GRB 100906A and GRB 101020A. These observations were made with the Mobile Astronomical System of TElescope-Robots in Russia (MASTER-II Net), the 1.5-m telescope of the Sierra Nevada Observatory and the 2.56-m Nordic Optical Telescope. For two sources, GRB 100901A and GRB 100906A, we detected optical counterparts and obtained light curves starting before the cessation of γ-ray emission, at 113 and 48 s after the trigger, respectively. Observations of GRB 100906A were conducted in two polarizing filters. Observations of the other three bursts gave the upper limits on the optical flux; their properties are briefly discussed. A more detailed analysis of GRB 100901A and GRB 100906A, supplemented by Swift data, provides the following results and indicates different origins for the prompt optical radiation in the two bursts. The light-curve patterns and spectral distributions suggest that there is a common production site for the prompt optical and high-energy emission in GRB 100901A. The results of the spectral fits for GRB 100901A in the range from optical to X-ray favour power-law energy distributions and a consistent value of the optical extinction in the host galaxy. GRB 100906A produced a smoothly peaking optical light curve, suggesting that the prompt optical radiation in this GRB originated in a front shock. This is supported by a spectral analysis. We have found that the Amati and Ghirlanda relations are satisfied for GRB 100906A. We obtain an upper limit on the value of the optical extinction on the host of GRB 100906A. Also we consider prompt observation of dark gamma ray bursts for which on very widefield cameras MASTER-VWF and MASTER-II telescopes upper limits were received. We represent SHOCK experiment onboard the spacecraft Lomonosov.

  9. On the Possibilities of Predicting Geomagnetic Secular Variation with Geodynamo Modeling

    Science.gov (United States)

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

    2004-01-01

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

  10. Observation of three dimensional optical rogue waves through obstacles

    Energy Technology Data Exchange (ETDEWEB)

    Leonetti, Marco, E-mail: marco.leonetti@roma1.infn.it [Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena, 291 00161 Roma (RM) (Italy); Conti, Claudio [ISC-CNR and Department of Physics, University Sapienza, P.le Aldo Moro 5, I-00185 Roma (Italy)

    2015-06-22

    We observe three-dimensional rogue waves in the speckle distribution of a spatially modulated optical beam. Light is transmitted beyond a partially reflecting obstacle generating optical rogue waves at a controlled position in the shadow of the barrier. When the barrier transmits only 0.07% of the input laser power, we observe the mostly localized event. These results demonstrate that an optimum amount of spatial non-homogeneity maximizes the probability of a gigantic event while the technique we exploit enables to control light behind a fully reflective wall.

  11. Optical technologies for the observation of low Earth orbit objects

    CERN Document Server

    Hampf, Daniel; Riede, Wolfgang

    2015-01-01

    In order to avoid collisions with space debris, the near Earth orbit must be continuously scanned by either ground- or spaced-based facilities. For the low Earth orbit, radar telescopes are the workhorse for this task, especially due to their continuous availability. However, optical observation methods can deliver complementary information, especially towards high accuracy measurements. Passive-optical observations are inexpensive and can yield very precise information about the apparent position of the object in the sky via comparison with background stars. However, the object's distance from the observer is not readily accessible, which constitutes a major drawback of this approach for the precise calculation of the orbital elements. Two experimental methods have been devised to overcome this problem: Using two observatories a few kilometres apart, strictly simultaneous observations of the same object yield an accurate, instantaneous 3D position determination through measurement of the parallax. If only on...

  12. On regional geomagnetic charts

    Science.gov (United States)

    Alldredge, L.R.

    1987-01-01

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

  13. On Geomagnetism and Paleomagnetism

    Science.gov (United States)

    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

  14. Optical telescope BIRT in ORIGIN for gamma ray burst observing

    DEFF Research Database (Denmark)

    Content, Robert; Sharples, Ray; Page, Mathew J.

    2012-01-01

    The ORIGIN concept is a space mission with a gamma ray, an X-ray and an optical telescope to observe the gamma ray bursts at large Z to determine the composition and density of the intergalactic matter in the line of sight. It was an answer to the ESA M3 call for proposal. The optical telescope i...... length. All 3 instruments use the same 2k x 2k detector simultaneously so that telescope pointing and tip-tilt control of a fold mirror permit to place the gamma ray burst on the desired instrument without any other mechanism. © 2012 SPIE....

  15. Navy Prototype Optical Interferometer observations of geosynchronous satellites.

    Science.gov (United States)

    Hindsley, Robert B; Armstrong, J Thomas; Schmitt, Henrique R; Andrews, Jonathan R; Restaino, Sergio R; Wilcox, Christopher C; Vrba, Frederick J; Benson, James A; DiVittorio, Michael E; Hutter, Donald J; Shankland, Paul D; Gregory, Steven A

    2011-06-10

    Using a 15.9  m baseline at the Navy Prototype Optical Interferometer (NPOI), we have successfully detected interferometric fringes in observations of the geosynchronous satellite (geosat) DirecTV-9S while it glinted on two nights in March 2009. The fringe visibilities can be fitted by a model consisting of two components, one resolved (≳3.7  m) and one unresolved (∼1.1  m). Both the length of the glint and the specular albedos are consistent with the notion that the glinting surfaces are not completely flat and scatter reflected sunlight into an opening angle of roughly 15°. Enhancements to the NPOI that would improve geosat observations include adding an infrared capability, which could extend the glint season, and adding larger, adaptive-optics equipped telescopes. Future work may test the feasibility of observing geosats with aperture-masked large telescopes and of developing an array of six to nine elements.

  16. The Small Size Debris Population at GEO from Optical Observations

    Science.gov (United States)

    Seitzer, Patrick; Barker, Ed; Buckalew, Brent; Burkhardt, Andrew; Cowardin, Heather; Frith, James; Kaleida, Catherine; Lederer, Susan M.; Lee, Chris H.

    2017-01-01

    We have observed the geosynchronous orbit (GEO) debris population at sizes smaller than 10 cm using optical observations with the 6.5-m Magellan telescope 'Walter Baade' at the Las Campanas Observatory in Chile. The IMACS f/2 imaging camera with a 0.5-degree diameter field of view has been used in small area surveys of the GEO regime to study the population of optically faint GEO debris. The goal is to estimate the population of GEO debris that is fainter than can be studied with 1-meter class telescopes. A significant population of objects fainter than R = 19th magnitude has been found. These objects have observed with angular rates consistent with circular orbits and orbital inclinations up to 15 degrees at GEO. A sizeable number of these objects have significant brightness variations ("flashes") during the 5-second exposure, which suggest rapid changes in the albedo-projected size product.

  17. Optical Properties of Volcanic Ash: Improving Remote Sensing Observations

    Science.gov (United States)

    Whelley, P.; Colarco, P. R.; Aquila, V.; Krotkov, N. A.; Bleacher, J. E.; Garry, W. B.; Young, K. E.; Lima, A. R.; Martins, J. V.; Carn, S. A.

    2015-12-01

    Many times each year explosive volcanic eruptions loft ash into the atmosphere. Global travel and trade rely on aircraft vulnerable to encounters with airborne ash. Volcanic ash advisory centers (VAACs) rely on dispersion forecasts and satellite data to issue timely warnings. To improve ash forecasts model developers and satellite data providers need realistic information about volcanic ash microphysical and optical properties. In anticipation of future large eruptions we can study smaller events to improve our remote sensing and modeling skills so when the next Pinatubo 1991 or larger eruption occurs, ash can confidently be tracked in a quantitative way. At distances >100km from their sources, drifting ash plumes, often above meteorological clouds, are not easily detected from conventional remote sensing platforms, save deriving their quantitative characteristics, such as mass density. Quantitative interpretation of these observations depends on a priori knowledge of the spectral optical properties of the ash in UV (>0.3μm) and TIR wavelengths (>10μm). Incorrect assumptions about the optical properties result in large errors in inferred column mass loading and size distribution, which misguide operational ash forecasts. Similarly, simulating ash properties in global climate models also requires some knowledge of optical properties to improve aerosol speciation. Recent research has identified a wide range in volcanic ash optical properties among samples collected from the ground after different eruptions. The database of samples investigated remains relatively small, and measurements of optical properties at the relevant particle sizes and spectral channels are far from complete. Generalizing optical properties remains elusive, as does establishing relationships between ash composition and optical properties, which are essential for satellite retrievals. We are building a library of volcanic ash optical and microphysical properties. In this presentation we show

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

    Science.gov (United States)

    Voorhies, Coerte V.

    1992-01-01

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

  19. Speckle reconstruction of photometric data observed with adaptive optics

    OpenAIRE

    Puschmann, K. G.; Sailer, M

    2006-01-01

    To achieve the highest spatial resolution for ground-based observations one has to correct for degradations by the Earth’s atmosphere. This can be done by on-line and post-facto techniques. Here we combine observations with Adaptive Optics (AO) and speckle reconstruction. As possible techniques we present two modified versions (methods B and C) of the Göttingen speckle masking code and describe their application to observations of a solar active region obtained with the Swedish 1-m S...

  20. The Burst Observer and Optical Transient Exploring System (BOOTES)

    Science.gov (United States)

    Castro-Tirado, A. J.; Soldán, J.; Bernas, M.; Páta, P.; Rezek, T.; Hudec, R.; Mateo Sanguino, T. J.; de La Morena, B.; Berná, J. A.; Rodríguez, J.; Peña, A.; Gorosabel, J.; Más-Hesse, J. M.; Giménez, A.

    1999-09-01

    The Burst Observer and Optical Transient Exploring System (BOOTES) is considered as a part of the preparations for the ESA's satellite INTEGRAL, and is currently being developed in Spain, in collaboration with two Czech institutions. It makes use of two sets of wide-field cameras 240 kms apart, and two robotic 0.3-m telescopes. The first observing station (BOOTES-1) is located in Huelva (Spain) and the first light was obtained in July 1998. During the test phase, it has provided rapid follow-up observations for 5 GRBs detected by the BATSE aboard the CGRO. The system will fully operate in late 1999.

  1. Geomagnetic storms: historical perspective to modern view

    Science.gov (United States)

    Lakhina, Gurbax S.; Tsurutani, Bruce T.

    2016-12-01

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

  2. Binary stars observed with adaptive optics at the starfire optical range

    Energy Technology Data Exchange (ETDEWEB)

    Drummond, Jack D. [Air Force Research Laboratory, Directed Energy Directorate, RDSAM, 3550 Aberdeen Avenue SE, Kirtland AFB, NM 87117-5776 (United States)

    2014-03-01

    In reviewing observations taken of binary stars used as calibration objects for non-astronomical purposes with adaptive optics on the 3.5 m Starfire Optical Range telescope over the past 2 years, one-fifth of them were found to be off-orbit. In order to understand such a high number of discrepant position angles and separations, all previous observations in the Washington Double Star Catalog for these rogue binaries were obtained from the Naval Observatory. Adding our observations to these yields new orbits for all, resolving the discrepancies. We have detected both components of γ Gem for the first time, and we have shown that 7 Cam is an optical pair, not physically bound.

  3. Bi-static Optical Observations of GEO Objects

    Science.gov (United States)

    Seitzer, Patrick; Barker, Edwin S.; Cowardin, Heather; Lederer, Susan M.; Buckalew, Brent

    2014-01-01

    A bi-static study of objects at Geosynchronous Earth Orbit (GEO) was conducted using two ground-based wide-field optical telescopes. The University of Michigan's 0.6-m MODEST (Michigan Orbital Debris Survey Telescope) located at the Cerro Tololo Inter- American Observatory in Chile was employed in a series of coordinated observations with the U.S. Naval Observatory's (USNO) 1.3-m telescope at the USNO Flagstaff Station near Flagstaff, Arizona, USA. The goals of this project are twofold: (1) Obtain optical distances to known and unknown objects at GEO from the difference in the observed topocentric position of objects measured with respect to a reference star frame. The distance can be derived directly from these measurements, and is independent of any orbital solution. The wide geographical separation of these two telescopes means that the parallax difference is larger than ten degrees, and (2) Compare optical photometry in similar filters of GEO objects taken during the same time period from the two sites. The object's illuminated surfaces presented different angles of reflected sunlight to the two telescopes.During a four hour period on the night.of 22 February 2014 (UT), coordinated observations were obtained for eight different GEO positions. Each coordinated observation sequence was started on the hour or half-hour, and was selected to ensure the same cataloged GEO object was available in the field of view of both telescopes during the thirty minute observing sequence. GEO objects were chosen to be both controlled and uncontrolled at a range of orbital inclinations, and the objects were not tracked. Instead both telescopes were operated with all drives off in GEO survey mode to discover un-cataloged objects at GEO. The initial results from this proof-of-concept observing run will be presented, with the intent of laying the foundation for future large-scale bi-static observing campaigns of the GEO regime.

  4. Experimental observation of polarization-dependent optical vortex beams

    CERN Document Server

    Srisuphaphon, S; Photia, T; Temnuch, W; Chiangga, S; Deachapunya, S

    2016-01-01

    We report the experimental demonstration of the induced polarization-dependent optical vortex beams. We use the Talbot configuration as a method to probe this effect. In particular, our simple experiment shows the direct measurement of this observation. Our experiment can exhibit clearly the combination between the polarization and orbital angular momentum (OAM) states of light. This implementation might be useful for further studies in the quantum system or quantum information.

  5. Optical Observations of PSR J0205+6449 - the next optical pulsar?

    CERN Document Server

    Moran, P; Collins, S; de Luca, A; Rea, N; Shearer, A

    2013-01-01

    PSR J0205+6449 is a young ({\\approx} 5400 years), Crab-like pulsar detected in radio and at X and {\\gamma}-ray energies and has the third largest spin-down flux among known rotation powered pulsars. It also powers a bright synchrotron nebula detected in the optical and X-rays. At a distance of {\\approx} 3.2 kpc and with an extinction comparable to the Crab, PSR J0205+6449 is an obvious target for optical observations. We observed PSR J0205+6449 with several optical facilities, including 8m class ground-based telescopes, such as the Gemini and the Gran Telescopio Canarias. We detected a point source, at a significance of 5.5{\\sigma}, of magnitude i {\\approx} 25.5, at the centre of the optical synchrotron nebula, coincident with the very accurate Chandra and radio positions of the pulsar. Thus, we discovered a candidate optical counterpart to PSR J0205+6449. The pulsar candidate counterpart is also detected in the g ({\\approx}27.4) band and weakly in the r ({\\approx}26.2) band. Its optical spectrum is fit by a ...

  6. WIDGET: System Performance and GRB Prompt Optical Observations

    CERN Document Server

    Urata, Yuji; Tamagawa, Toru; Usui, Fumihiko; Kuwahara, Makoto; Lin, Hungmiao; Kageyama, Shoichi; Iwakiri, Wataru; Sugasahara, Takako; Takahara, Kazuki; Kodaka, Natsuki; Abe, Keiichi; Masuno, Keisuke; Onda, Kaori

    2010-01-01

    The WIDeField telescope for Gamma-ray burst Early Timing (WIDGET) is used for a fully automated, ultra-wide-field survey aimed at detecting the prompt optical emission associated with Gamma-ray Bursts (GRBs). WIDGET surveys the HETE-2 and Swift/BAT pointing directions covering a total field of view of 62 degree x 62 degree every 10 secounds using an unfiltered system. This monitoring survey allows exploration of the optical emission before the gamma-ray trigger. The unfiltered magnitude is well converted to the SDSS r' system at a 0.1 mag level. Since 2004, WIDGET has made a total of ten simultaneous and one pre-trigger GRB observations. The efficiency of synchronized observation with HETE-2 is four times better than that of Swift. There has been no bright optical emission similar to that from GRB 080319B. The statistical analysis implies that GRB080319B is a rare event. This paper summarizes the design and operation of the WIDGET system and the simultaneous GRB observations obtained with this instrument.

  7. Remote Sensing of Geomagnetic Field and Applications to Climate Prediction

    CERN Document Server

    Selvam, A M

    2000-01-01

    Observations show that geomagnetic field lines follow closely the atmosphericcirculation patterns and that geomagnetic field variations are precursors toclimate change . The exact mechanism for the observed close relationshipbetween global geomagnetic field and the tropospheric weather patterns is notclear. In this paper a universal theory of atmospheric eddy dynamics ispresented which shows that the global geomagnetic field, atmospheric electricfield and weather systems are manifestations of a semi permanent scaleinvariant hierarchical atmospheric eddy continuum. Quantitative equations arederived to show that the full continuum of atmospheric eddies exist as aunified whole and originate from buoyant energy supply from frictionalturbulence at the planetary surface . Large eddy growth occurs from turbulencescale by the universal period doubling route to chaos . The turbulent eddiesare carried upwards on the large eddy envelopes and vertical mixing occurs bythe turbulent eddy fluctuations resulting in downward ...

  8. Studies on the Geomagnetic Induction Vectors of China

    Science.gov (United States)

    Wang, Qiao; Zhang, Huiqian; Huang, Qinghua

    2016-04-01

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

  9. Hazards of geomagnetic storms

    Science.gov (United States)

    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. 

  10. High Resolution Observations using Adaptive Optics: Achievements and Future Needs

    Indian Academy of Sciences (India)

    K. Sankarasubramanian; T. Rimmele

    2008-03-01

    Over the last few years, several interesting observations were obtained with the help of solar Adaptive Optics (AO). In this paper, few observations made using the solarAOare enlightened and briefly discussed. A list of disadvantages with the current AO system are presented. With telescopes larger than 1.5 m expected during the next decade, there is a need to develop the existing AO technologies for large aperture telescopes. Some aspects of this development are highlighted. Finally, the recent AO developments in India are also presented.

  11. Optical Observations of the Transiting Exoplanet GJ 1214b

    CERN Document Server

    Teske, Johanna K; Mueller, Matthias; Griffith, Caitlin A

    2013-01-01

    We observed nine primary transits of the super-Earth exoplanet GJ 1214b in several optical photometric bands from March to August 2012, with the goal of constraining the short-wavelength slope of the spectrum of GJ 1214b. Our observations were conducted on the Kuiper 1.55 m telescope in Arizona and the STELLA-I robotic 1.2 m telescope in Tenerife, Spain. From the derived light curves we extracted transit depths in R (0.65 {\\mu}m), V (0.55 {\\mu}m), and g' (0.475 {\\mu}m) bands. Most previous observations of this exoplanet suggest a flat spectrum varying little with wavelength from the near-infrared to the optical, corresponding to a low-scale-height, high-molecular-weight atmosphere. However, a handful of observations around Ks band (~2.15 {\\mu}m) and g-band (~0.46 {\\mu}m) are inconsistent with this scenario and suggest a variation on a hydrogen- or water-dominated atmosphere that also contains a haze layer of small particles. In particular, the g-band observations of de Mooij et al. (2012), consistent with Ray...

  12. Optical SETI Observations of the Anomalous Star KIC 8462852

    Science.gov (United States)

    Schuetz, Marlin; Vakoch, Douglas A.; Shostak, Seth; Richards, Jon

    2016-07-01

    To explore the hypothesis that KIC 8462852's aperiodic dimming is caused by artificial megastructures in orbit, rather than a natural cause such as cometary fragments in a highly elliptical orbit, we searched for electromagnetic signals from KIC 8462852 indicative of extraterrestrial intelligence. The primary observations were in the visible optical regime using the Boquete Optical SETI Observatory in Panama. In addition, as a recommended preparatory exercise for the possible future detection of a candidate signal, three of six observing runs simultaneously searched radio frequencies at the Allen Telescope Array in California. No periodic optical signals greater than 67 photons m-2 within a time frame of 25 ns were seen. If, for example, any inhabitants of KIC 8462852 were targeting our solar system with 5 MJ laser pulses, locally illuminating an approximately 3 au diameter disk, the signal could have been detected at the Boquete Observatory. The limits on narrowband radio signals were 180-300 Jy Hz at 1 and 8 GHz, respectively. While the power requirement for a detectable, isotropic narrowband radio transmission from KIC 8462852 is quite high, even modest targeting on the part of the putative extraterrestrials can lower this power substantially.

  13. RAPTOR observations of the early optical afterglow from GRB 050319

    CERN Document Server

    Wozniak, P R; Wren, J A; White, R R; Evans, S M; Casperson, D

    2005-01-01

    The RAPid Telescopes for Optical Response (RAPTOR) system at Los Alamos National Laboratory observed GRB 050319 starting 25.4 seconds after gamma-ray emission triggered the Burst Alert Telescope (BAT) on-board the Swift satellite. Our well sampled light curve of the early optical afterglow is composed of 32 points (derived from 70 exposures) that measure the flux decay during the first hour after the GRB. The GRB 050319 light curve measured by RAPTOR can be described as a relatively gradual flux decline (power-law index alpha = -0.37) with a transition, at about 400 s after the GRB, to a faster flux decay (alpha = -0.91). The addition of other available measurements to the RAPTOR light curve suggests that another emission component emerged after 10^4 s. We hypothesize that the early afterglow emission is powered by extended energy injection or delayed reverse shock emission followed by the emergence of forward shock emission.

  14. Characterization and compensation of thermo-elastic instability of SWARM optical bench on micro Advanced Stellar Compass attitude observations

    Science.gov (United States)

    Herceg, M.; Jørgensen, P. S.; Jørgensen, J. L.

    2017-08-01

    Launched into orbit on November 22, 2013, the Swarm constellation of three satellites precisely measures magnetic signal of the Earth. To ensure the high accuracy of magnetic observation by vector magnetometer (VFM), its inertial attitude is precisely determined by μASC (micro Advanced Stellar Compass). Each of the three Swarm satellites is equipped with three μASC Camera Head Units (CHU) mounted on a common optical bench (OB), which has a purpose of transference of the attitude from the star trackers to the magnetometer measurements. Although substantial pre-launch analyses were made to maximize thermal and mechanical stability of the OB, significant signal with thermal signature is discovered when comparing relative attitude between the three CHU's (Inter Boresight Angle, IBA). These misalignments between CHU's, and consequently geomagnetic reference frame, are found to be correlated with the period of angle between Swarm orbital plane and the Sun (ca. 267 days), which suggests sensitivity of optical bench system on temperature variation. In this paper, we investigate the propagation of thermal effects into the μASC attitude observations and demonstrate how thermally induced attitude variation can be predicted and corrected in the Swarm data processing. The results after applying thermal corrections show decrease in IBA RMS from 6.41 to 2.58″. The model significantly improves attitude determination which, after correction, meets the requirements of Swarm satellite mission. This study demonstrates the importance of the OB pre-launch analysis to ensure minimum thermal gradient on satellite optical system and therefore maximum attitude accuracy.

  15. Dependence of geosynchronous relativistic electron enhancements on geomagnetic parameters

    CERN Document Server

    Dmitriev, A V

    2014-01-01

    Relativistic electron fluxes observed in geosynchronous orbit by GOES-8 in 1997 to 2000 were considered as a complex function of geomagnetic indices PC, Kp, and Dst as well as parameters of the magnetosphere size, subsolar Rs and terminator Rf magnetopause distances. A geosynchronous relativistic electron enhancement (GREE) is determined as daily maximal electron flux exceeding the upper root mean square deviation (RMSD) threshold of about 1500 (cm2s sr)-1. Comparison analysis of the GREE dynamics and geomagnetic conditions on the rising phase of current solar cycle revealed suppression of the relativistic electron enhancements by substantially increased strong geomagnetic activity in the solar maximum. Statistical consideration of a relationship between the GREEs and the geomagnetic parameters showed that the most important parameters controlling the geosynchronous relativistic electron enhancements were 4-day averaged Kp index, PC index and magnetopause termination distance Rf delayed respectively on 3 and ...

  16. Human physiological reaction to geomagnetic disturbances of solar origin

    Science.gov (United States)

    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.

  17. Geographical localisation of the geomagnetic secular variation

    OpenAIRE

    Aubert, Julien; Finlay, Chris; Olsen, Nils

    2013-01-01

    Directly observed changes in Earth’s magnetic field occur most prominently at low latitudes beneath the Atlantic hemisphere, while the Pacific is comparatively quiet. This striking hemispheric asymmetry in geomagnetic secular variation is a consequence of the geographical localisation of intense, westward moving, magnetic flux patches at the core surface. Despite its successes in explaining the main morphological properties of Earth’s magnetic field, self-consistent numerical modelling of the...

  18. Ultraviolet and optical observations of tidal disruption events

    Directory of Open Access Journals (Sweden)

    Gezari S.

    2012-12-01

    Full Text Available Tidal disruption events are expected to produce a luminous flare of radiation from fallback accretion of tidally disrupted stellar debris onto the central supermassive black hole. The first convincing candidates for tidal disruption events were discovered in the soft X-rays: large-amplitude, luminous, extremely-soft X-ray flares from inactive galaxies in the ROSAT All-Sky survey. However, the sparsely sampled light curves and lack of multiwavelength observations for these candidates make it difficult to directly constrain the parameters of their events (e.g., Eddington ratio, mass of the black hole, type of star disrupted. Here I present a review of the recent progress made in studying tidal disruption events in detail from taking advantage of wide-field, multi-epoch observations of UV and optical surveys (GALEX, SDSS, PTF, Pan-STARRS1 to measure well-sampled light curves, trigger prompt multiwavelength follow-up observations, and measure rates. I conclude with the promising potential of the next generation of optical synoptic surveys, such as LSST, to probe black hole demographics with samples of thousands of tidal disruption events.

  19. Multifractal analysis of low-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    M. J. A. Bolzan

    2009-02-01

    Full Text Available 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.

  20. Effects of geomagnetic activity on the mesospheric electric fields

    Directory of Open Access Journals (Sweden)

    A. M. Zadorozhny

    Full Text Available The results of three series of rocket measurements of mesospheric electric fields carried out under different geomagnetic conditions at polar and high middle latitudes are analysed. The measurements show a clear dependence of the vertical electric fields on geomagnetic activity at polar and high middle latitudes. The vertical electric fields in the lower mesosphere increase with the increase of geomagnetic indexes Kp and ∑Kp. The simultaneous increase of the vertical electric field strength and ion conductivity was observed in the mesosphere during geomagnetic disturbances. This striking phenomenon was displayed most clearly during the solar proton events of October, 1989 accompanied by very strong geomagnetic storm (Kp=8+. A possible mechanism of generation of the vertical electric fields in the mesosphere caused by gravitational sedimentation of charged aerosol particles is discussed. Simultaneous existence in the mesosphere of both the negative and positive multiply charged aerosol particles of different sizes is assumed for explanation of the observed V/m vertical electric fields and their behaviour under geomagnetically disturbed conditions.

    Keywords. Atmospheric composition and structure (aerosols and particles · Ionosphere (electric fields and currents · Meteorology and atmospheric dynamics (atmospheric electricity

  1. Stellar populations from adaptive optics observations four test cases

    CERN Document Server

    Bedding, T R; Courbin, F; Sams, B J

    1997-01-01

    We describe a first attempt to apply adaptive optics to the study of resolved stellar populations in galaxies. Advantages over traditional approaches are (i) improved spatial resolution and point-source sensitivity through adaptive optics, and (ii) use of the near-infrared region, where the peak of the spectral energy distribution for old populations is found. Disadvantages are the small area covered and the need for excellent seeing. We made observations with the ADONIS system at the European Southern Observatory of the peculiar elliptical galaxy NGC 5128; the irregular galaxy IC 5152 (a possible outer member of the Local Group); the Sc galaxy NGC 300 (a member of the Sculptor group); and the Sgr window in the bulge of the Milky Way. These different fields give excellent test cases for the potential of adaptive optics. In the first two cases, we failed to obtain photometry of individual stars, which would have required excellent seeing. For NGC 300 we measured magnitudes for nine individual supergiants (H = ...

  2. Optical observation of supernova remnant in elliptical galaxy NGC 185

    Science.gov (United States)

    Vučetić, M.; Arbutina, B.; Pavlovic, M. Z.; Ciprijanovic, A.; Urosevic, D.; Petrov, N.; Onić, D.; Trcka, A.

    2016-06-01

    In this paper we discuss the previously known optical supernova remnant (SNR) in NGC 185 galaxy, a dwarf elliptical companion of the Andromeda galaxy, in order to gain more information about its properties and evolutionary status. To this end, we observed a central portion of NGC 185, through the narrowband Hα and [SII]} filters, on a 2m RCC-telescope at National astronomical observatory Rozhen, Bulgaria. Also, we performed MHD simulations using the Pluto code, for the case of low environmental density and high pressure, in order to discuss evolution of a SNR in a gas poor dwarf galaxy.

  3. Bayesian inference in geomagnetism

    Science.gov (United States)

    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.

  4. Geomagnetic observatories: monitoring the Earth’s magnetic and space weather environment

    OpenAIRE

    Thomson, Alan W.P.

    2014-01-01

    Geomagnetism research provides insight into the Earth’s properties and processes, from the core out to space. For this reason continuous geomagnetic field observations have been carried out in the UK for more than 170 years. Geomagnetism also has diverse applications, in navigation, maps, even smart phone apps, and in the monitoring and prediction of space weather impacts on technology. Modern instruments, together with digital sampling, real-time data processing and product dissemination, su...

  5. Optical, infrared and radio astronomy from techniques to observation

    CERN Document Server

    Poggiani, Rosa

    2017-01-01

    This textbook presents the established sciences of optical, infrared, and radio astronomy as distinct research areas, focusing on the science targets and the constraints that they place on instrumentation in the different domains. It aims to bridge the gap between specialized books and practical texts, presenting the state of the art in different techniques. For each type of astronomy, the discussion proceeds from the orders of magnitude for observable quantities that drive the building of instrumentation and the development of advanced techniques. The specific telescopes and detectors are then presented, together with the techniques used to measure fluxes and spectra. Finally, the instruments and their limits are discussed to assist readers in choice of setup, planning and execution of observations, and data reduction. The volume also includes worked examples and problem sets to improve student understanding; tables and figures in chapters summarize the state of the art of instrumentation and techniques.

  6. Geomagnetic Jerks in the Swarm Era

    Science.gov (United States)

    Brown, William; Beggan, Ciaran; Macmillan, Susan

    2016-08-01

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

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

    CERN Document Server

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

    2011-01-01

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

  8. Geomagnetic Observatory Database February 2004

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA National Centers for Environmental Information (formerly National Geophysical Data Center) maintains an active database of worldwide geomagnetic observatory...

  9. Geomagnetic Field Variation during Winter Storm at Localized Southern and Northern High Latitude

    Indian Academy of Sciences (India)

    Babita Devi; Smita Dubey; Shailendra Saini; Rajni Devi; Rashmi Wahi; Ajay Dhar; S. K. Vijay; A. K. Gwal

    2008-03-01

    This paper presents the effect of geomagnetic storm on geomagnetic field components at Southern (Maitri) and Northern (Kiruna) Hemispheres. The Indian Antarctic Station Maitri is located at geom. long. 66.03° S; 53.21° E whereas Kiruna is located at geom. long. 67.52° N; 23.38° E. We have studied all the geomagnetic storms that occurred during winter season of the year 2004–2005. We observed that at Southern Hemisphere the variation is large as compared to the Northern Hemisphere. Geomagnetic field components vary when the interplanetary magnetic field is oriented in southward direction. Geomagnetic field components vary in the main phase of the ring current. Due to southward orientation of vertical component of IMF reconnection takes place all across the dayside that transports plasma and magnetic flux which create the geomagnetic field variation.

  10. On polar daily geomagnetic variation

    Directory of Open Access Journals (Sweden)

    Paola De Michelis

    2015-11-01

    Full Text Available The aim of this work is to investigate the nature of the daily magnetic field perturbations produced by ionospheric and magnetospheric currents at high latitudes. We analyse the hourly means of the X and Y geomagnetic field components recorded by a meridian chain of permanent geomagnetic observatories in the polar region of the Northern Hemisphere during a period of four years (1995-1998 around the solar minimum. We apply a mathematical method, known as natural orthogonal component (NOC, which is capable of characterizing the dominant modes of the geomagnetic field daily variability through a set of empirical orthogonal functions (EOFs. Using the first two modes we reconstruct a two-dimensional equivalent current representation of the ionospheric electric currents, which contribute substantially to the geomagnetic daily variations. The obtained current structures resemble the equivalent current patterns of DP2 and DP1. We characterize these currents by studying their evolution with the geomagnetic activity level and by analysing their dependence on the interplanetary magnetic field. The obtained results support the idea of a coexistence of two main processes during all analysed period although one of them, the directly driven process, represents the dominant component of the geomagnetic daily variation.

  11. The correlations of ions density with geomagnetic activity and solar dynamic pressure in cusp region

    Institute of Scientific and Technical Information of China (English)

    GUO JianGuang; SHI JianKui; ZHANG TieLong; LIU ZhenXing; A. FAZAKERLEY; H. R(E)ME; Ⅰ. DANDOURAS; E. LUCEK

    2007-01-01

    A statistical study of the properties of ions (O+, He+ and H+) measured by the Cluster-Ⅱ in cusp region as a function of the solar wind dynamic pressure and geomagnetic index Kp respectively was made during the summer and fall of 2001 -2003. The main results are that: (1) O+ ion density responds in a significant way to geomagnetic index Kp, and He+ ion density is not correlated with geomagnetic index Kp,both of them have a significant positive correlation with solar wind dynamic pressure; (2) H+ ion density is also observed to increase with solar wind dynamic pressure, and not correlated with geomagnetic index Kp.

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

    CERN Document Server

    Selvam, A M; Athale, S U; Tinmaker, M I R

    1998-01-01

    Observational studies indicate that there is a close association between geomagnetic storm and meteorological parameters. Geomagnetic field lines follow closely the isobars of surface pressure . A Physical mechanism linking upper atmospheric geomagnetic storm disturbances with tropospheric weather has been proposed by the author and her group where it is postulated that vertical mixing by turbulent eddy fluctuations results in the net transport upward of positive charges originating from lower levels accompanied simultaneously by downward flow of negative charges from higher levels. The present study reports enhancement of high frequency (<15 days period) fluctuations in daily surface pressure during March 1989 in association with major geomagnetic storm (Ap index = 246) on 13 march 1989.

  13. Topological photonics: an observation of Landau levels for optical photons

    Science.gov (United States)

    Schine, Nathan; Ryou, Albert; Sommer, Ariel; Simon, Jonathan

    Creating photonic materials with nontrivial topological characteristics has seen burgeoning interest in recent years; however, a major route to topology, a magnetic field for continuum photons, has remained elusive. We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We will discuss the conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids. This work was supported by DOE, DARPA, and AFOSR.

  14. Global Terrestrial Evapotranspiration from Optical and Microwave Satellite Observations

    Science.gov (United States)

    Jia, Li; Zhang, Chaolei; Hu, Guangcheng; Zhou, Jie; Cui, Yaokui; Lu, Jing; Wang, Kun; Liu, Qinhuo; Menenti, Massimo

    2016-08-01

    Terrestrial actual evapotranspiration (ET) is an important component of the terrestrial water cycle and links the hydrological, energy, and carbon cycles. Considering the diverse landscapes and multi-climatic features, a hybrid remotely sensed ET estimation model named ETMonitor was developed to estimate the daily actual evapotranspiration globally at a spatial resolution of 1 km. The ETMonitor model uses a variety of biophysical parameters derived from microwave and optical remote sensing observations as input data to estimate the daily ET for all sky conditions. This dataset provides important support to the large-scale evaluation of the environment, and some preliminary applications were conducted for regional- to global-scale mapping and monitoring of water consumption and drought severity.

  15. Radio & Optical Interferometry: Basic Observing Techniques and Data Analysis

    CERN Document Server

    Monnier, John D

    2012-01-01

    Astronomers usually need the highest angular resolution possible, but the blurring effect of diffraction imposes a fundamental limit on the image quality from any single telescope. Interferometry allows light collected at widely-separated telescopes to be combined in order to synthesize an aperture much larger than an individual telescope thereby improving angular resolution by orders of magnitude. Radio and millimeter wave astronomers depend on interferometry to achieve image quality on par with conventional visible and infrared telescopes. Interferometers at visible and infrared wavelengths extend angular resolution below the milli-arcsecond level to open up unique research areas in imaging stellar surfaces and circumstellar environments. In this chapter the basic principles of interferometry are reviewed with an emphasis on the common features for radio and optical observing. While many techniques are common to interferometers of all wavelengths, crucial differences are identified that will help new practi...

  16. The triangulation of the gigantic jets observed by the optical observation network in Taiwan

    Science.gov (United States)

    Chen, Alfred B.; Huang, Chien-Fong; Peng, Kang-Ming; Su, Han-Tzong; Hsu, Rue-Ron

    2015-04-01

    The optical triangulation of sprites and elves by the multiple sites has been done in the past decades, but the similar observation on gigantic jets has never been reported yet. A ground optical observation network consisting of four stations at Kimen, Penghu, Tainan, and Taitung (from west to east) has been established in Taiwan since 2012. Each station equipped with two sets of Watec low-light sensitivity cameras, and the elevation and azimuth of the observation can be fully remote controlled to point toward the on-going convection system in the vicinity of Taiwan. In summer 2014, more than 6 gigantic jets were captured by at least two stations successfully. The triangulation and ULF sferics of these interesting events provides an excellent chance to explore the spatial and temporal evolution of the jets in different phases. In this presentation, this ground observation network will be introduced, the detail evolution of the recorded gigantic jets is presented. The preliminary result implies that the jets may not pop from the cloudtop straightforwardly, and some twists occur during the propagation of the jets. A more complicated analysis of the tomography for the advanced triangulation will be mentioned, too.

  17. Experimental observation of optical differentiation and optical Hilbert transformation using a single SOI microdisk chip

    CERN Document Server

    Yang, Ting; Liu, Li; Liao, Shasha; Tan, Sisi; Shi, Lei; Gao, Dingshan; Zhang, Xinliang

    2013-01-01

    Optical differentiation and optical Hilbert transformation play important roles in communications, computing, information processing and signal analysis in optical domain which offering huge bandwidth. Meanwhile, silicon-based photonic integrated circuits are preferable in all-optical signal processing due to their intrinsic advantages of low power consumption, compact footprint and ultra-high speed. In this study, we analyze the interrelation between first-order optical differentiation and optical Hilbert transformation and then experimentally demonstrate a feasible integrated scheme which can simultaneously function as first-order optical differentiation and optical Hilbert transformation based on a single microdisk resonator. This finding may motivate the development of integrated optical signal processors.

  18. Ionospheric redistribution during geomagnetic storms.

    Science.gov (United States)

    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 (Dststorm 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. SOAR Adaptive Optics Observations of the Globular Cluster NGC 6496

    Science.gov (United States)

    Fraga, Luciano; Kunder, Andrea; Tokovinin, Andrei

    2013-06-01

    We present high-quality BVRI photometric data in the field of globular cluster NGC 6496 obtained with the SOAR Telescope Adaptive Module (SAM). Our observations were collected as part of the ongoing SAM commissioning. The distance modulus and cluster color excess as found from the red clump are (m - M) V = 15.71 ± 0.02 mag and E(V - I) = 0.28 ± 0.02 mag. An age of 10.5 ± 0.5 Gyr is determined from the difference in magnitude between the red clump and the subgiant branch. These parameters are in excellent agreement with the values derived from isochrone fitting. From the color-magnitude diagram we find a metallicity of [Fe/H] = -0.65 dex and hence support a disk classification for NGC 6496. The complete BVRI data set for NGC 6469 is made available in the electronic edition of the Journal. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  20. All-optical observation and reconstruction of spin wave dispersion

    Science.gov (United States)

    Hashimoto, Yusuke; Daimon, Shunsuke; Iguchi, Ryo; Oikawa, Yasuyuki; Shen, Ka; Sato, Koji; Bossini, Davide; Tabuchi, Yutaka; Satoh, Takuya; Hillebrands, Burkard; Bauer, Gerrit E. W.; Johansen, Tom H.; Kirilyuk, Andrei; Rasing, Theo; Saitoh, Eiji

    2017-06-01

    To know the properties of a particle or a wave, one should measure how its energy changes with its momentum. The relation between them is called the dispersion relation, which encodes essential information of the kinetics. In a magnet, the wave motion of atomic spins serves as an elementary excitation, called a spin wave, and behaves like a fictitious particle. Although the dispersion relation of spin waves governs many of the magnetic properties, observation of their entire dispersion is one of the challenges today. Spin waves whose dispersion is dominated by magnetostatic interaction are called pure-magnetostatic waves, which are still missing despite of their practical importance. Here, we report observation of the band dispersion relation of pure-magnetostatic waves by developing a table-top all-optical spectroscopy named spin-wave tomography. The result unmasks characteristics of pure-magnetostatic waves. We also demonstrate time-resolved measurements, which reveal coherent energy transfer between spin waves and lattice vibrations.

  1. Optical telescope BIRT in ORIGIN for gamma ray burst observing

    Science.gov (United States)

    Content, Robert; Sharples, Ray; Page, Mathew J.; Cole, Richard; Walton, David M.; Winter, Berend; Pedersen, Kristian; Hjorth, Jens; Andersen, Michael; Hornstrup, Allan; den Herder, Jan-Willem A.; Piro, Luigi

    2012-09-01

    The ORIGIN concept is a space mission with a gamma ray, an X-ray and an optical telescope to observe the gamma ray bursts at large Z to determine the composition and density of the intergalactic matter in the line of sight. It was an answer to the ESA M3 call for proposal. The optical telescope is a 0.7-m F/1 with a very small instrument box containing 3 instruments: a slitless spectrograph with a resolution of 20, a multi-imager giving images of a field in 4 bands simultaneously, and a cross-dispersed Échelle spectrograph giving a resolution of 1000. The wavelength range is 0.5 μm to 1.7 μm. All instruments fit together in a box of 80 mm x 80 mm x 200 mm. The low resolution spectrograph uses a very compact design including a special triplet. It contains only spherical surfaces except for one tilted cylindrical surface to disperse the light. To reduce the need for a high precision pointing, an Advanced Image Slicer was added in front of the high resolution spectrograph. This spectrograph uses a simple design with only one mirror for the collimator and another for the camera. The Imager contains dichroics to separate the bandwidths and glass thicknesses to compensate the differences in path length. All 3 instruments use the same 2k x 2k detector simultaneously so that telescope pointing and tip-tilt control of a fold mirror permit to place the gamma ray burst on the desired instrument without any other mechanism.

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

    Science.gov (United States)

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

    2014-06-01

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

  3. Prediction of solar particle events and geomagnetic activity using interplanetary scintillation observations from the iowa cocoa-cross radio telescope. Final report April 1, 1976--March 31, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Roelof, E.C.; Gotwols, B.L.; Mitchell, D.G.; Cronyn, W.M.; Shawhan, S.D.

    1978-05-01

    Synoptic interplanetary scintillation (IPS) observations were taken during the summer of 1976 and autumn of 1977 on the University of Iowa COCOA-Cross radio telescope (34.3 MHz), with supplementary observations from the University of Maryland TPT array (38 MHz). A new high sampling rate (10 times per second) digital system made it possible to reconstruct the IPS power spectrum between 0.1-3.0 Hz. The observations, combined with earlier (1974) measurements of integrated IPS power (scintillation index), have led to the conclusion (based on theoretical modelling) that prediction of activity and associated variations in energetic solar particle events is feasible with a lead time of about 24 hours. The technique depends on the observed broadening of the IPS power spectrum as solar wind density enhancements approach the earth. This effect has been documented for both co-rotating and solar flare-associated plasma disturbances.

  4. Features of the Geomagnetic Variations In the Moscow Region

    Science.gov (United States)

    Riabova, Svetlana; Spivak, Alexander

    2017-04-01

    The results of instrumental observations indicate the presence of significant amplitude variations in Earth's magnetic field. The data obtained in the research of geomagnetic variations allow us to not only establish and classify their sources, but also to form the basis for the improvement and development of new source models of magnetospheric and ionospheric disturbances, new methods of magnetotelluric and magnetovariational sensing and diagnostic methods of geodynamic state of the Earth's crust and the research of meteorological processes in the atmosphere. In this research we used the results of instrumental observations of geomagnetic field, carried out in the period of 2009 - 2015 at Geophysical Observatory "Mikhnevo" of Institute of Geosphere Dynamics of Russian Academy of Sciences. The observatory (54,960N; 37,774E) is located in the Moscow region. The analysis shows that in general the geophysical situation in the Moscow region is disturbed. The tendency to increasing in geomagnetic activity over time is established (the number of days with a perturbed state of the geomagnetic field is increased by 7.6 times during the period of 2009 - 2015). Repeatability of geomagnetic disturbances is characterized by clearly pronounced periodicity with characteristic periods of about 14, 27, 60, 182 and 365 days.

  5. Optical Turbulence Characterization at LAMOST Site: Observations and Models

    CERN Document Server

    Liu, L -Y; Yao, Y -Q; Vernin, J; Chadid, M; Wang, H -S; Yin, J; Wang, Y -P

    2015-01-01

    Atmospheric optical turbulence seriously limits the performance of high angular resolution instruments. An 8-night campaign of measurements was carried out at the LAMOST site in 2011, to characterize the optical turbulence. Two instruments were set up during the campaign: a Differential Image Motion Monitor (DIMM) used to measure the total atmospheric seeing, and a Single Star Scidar (SSS) to measure the vertical profiles of the turbulence C_n^2(h) and the horizontal wind velocity V(h). The optical turbulence parameters are also calculated with the Weather Research and Forecasting (WRF) model coupled with the Trinquet-Vernin model, which describes optical effects of atmospheric turbulence by using the local meteorological parameters. This paper presents assessment of the optical parameters involved in high angular resolution astronomy. Its includes seeing, isoplanatic angle, coherence time, coherence etendue, vertical profiles of optical turbulence intensity _n^2(h)$ and horizontal wind speed V(h). The median...

  6. Extreme geomagnetically induced currents

    Science.gov (United States)

    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.

  7. Preparing the optics technology to observe the hot universe

    DEFF Research Database (Denmark)

    Bavdaz, M.; Wille, Eric; Wallace, Kotska;

    2014-01-01

    is the Silicon Pore Optics (SPO) [1 to 23], a modular X-ray optics technology, which utilises processes and equipment developed for the semiconductor industry. The paper provides an overview of the programmatic background, the status of SPO technology and gives an outline of the development roadmap...... and activities undertaken and planned by ESA on optics, coatings [24 to 30] and test facilities [31, 33]....

  8. Observation of Amorphous Recording Marks Using Reflection-Mode Near-Field Scanning Optical Microscope Supported by Optical Interference Method

    Science.gov (United States)

    Sakai, Masaru; Mononobe, Shuji; Yusu, Keiichiro; Tadokoro, Toshiyasu; Saiki, Toshiharu

    2005-09-01

    A signal enhancing technique for a reflection-mode near-field scanning optical microscope (NSOM) is proposed. Optical interference between the signal light, from an aperture at the tip of a tapered optical fiber, and the reflected light, from a metallic coating around the aperture, enhances the signal intensity. We used a rewritable high-definition digital versatile disc (HD DVD) with dual recording layers as a sample medium, and demonstrated observation of amorphous recording marks on the semitransparent (the first) recording layer. In spite of low optical contrast between the crystal region and the amorphous region on this layer, we successfully observed recording marks with good contrast.

  9. MoSST DAS: The First Working Geomagnetic Data Assimilation System

    Science.gov (United States)

    Kuang, Weijia; Wei, Zigang; Tangborn, Andrew

    2011-01-01

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

  10. Optical polarization observations in the Scorpius region: NGC 6124

    CERN Document Server

    Vergne, M Marcela; Martinez, Ruben; Orsatti, Ana Maria; Alvarez, Maria Paula

    2010-01-01

    We have obtained optical multicolour (UBVRI) linear polarimetric data for 46 of the brightest stars in the area of the open cluster NGC 6124 in order to investigate the properties of the interstellar medium (ISM) that lies along the line of sight toward the cluster. Our data yield a mean polarization efficiency of $P_V/E_{B-V}=3.1\\pm$0.62, i.e., a value lower than the polarization produced by the ISM with normal efficiency for an average color excess of $E_{B-V}=0.80$ as that found for NGC 6124. Besides, the polarization shows an orientation of $\\theta \\sim 8^\\circ$.1 which is not parallel to the Galactic Disk,an effect that we think may be caused by the Lupus Cloud. Our analysis also indicates that the observed visual extinction in NGC 6124 is caused by the presence of three different absorption sheets located between the Sun and NGC 6124. The values of the internal dispersion of the polarization ($\\Delta P_V\\sim 1.3% $) and of the colour excess ($\\Delta E_{B-V}\\sim 0.29$ mag) for the members of NGC 6124 see...

  11. Keck Adaptive Optics Observations of TW Hydrae Association Members

    Energy Technology Data Exchange (ETDEWEB)

    Macintosh, B; Max, C; Zuckerman, B; Becklin, E E; Kaisler, D; Lowrance, P; Weinberger, A; Chirstou, J; Schneider, G; Acton, S

    2001-05-30

    Adaptive optics (AO) on 8-10 m telescopes is an enormously powerful tool for studying young nearby stars. It is especially useful for searching for companions. Using AO on the 10-m W.M. Keck II telescope we have measured the position of the brown dwarf companion to TWA5 and resolved the primary into an 0.055{double_prime} double. Over the next several years follow-up astrometry should permit an accurate determination of the masses of these young stars. We have also re-observed the candidate extrasolar planet TWAGB, but measurements of its motion relative to TWA6A are inconclusive. We are carrying out a search for new planetary or brown dwarf companions to TWA stars and, if current giant planet models are correct, are currently capable of detecting a 1 Jupiter-mass companion at {approx} 1.0{double_prime} and a 5 Jupiter-mass companion at {approx} 0.5{double_prime} around a typical TWA member.

  12. Optical polarization observations in the Scorpius region: NGC 6124

    Science.gov (United States)

    Vergne, M. Marcela; Feinstein, Carlos; Martínez, Ruben; Orsatti, Ana María; Alvarez, María Paula

    2010-04-01

    We have obtained optical multicolour (UBVRI) linear polarimetric data for 46 of the brightest stars in the area of the open cluster NGC 6124 in order to investigate the properties of the interstellar medium (ISM) that lies along the line of sight towards the cluster. Our data yield a mean polarization efficiency of PV/E(B - V) = 3.1 +/- 0.62, i.e. a value lower than the polarization produced by the ISM with normal efficiency for an average colour excess of E(B - V) = 0.80 as that found for NGC 6124. Besides, the polarization shows an orientation of which is not parallel to the Galactic disc, an effect that we think may be caused by the Lupus cloud. Our analysis also indicates that the observed visual extinction in NGC 6124 is caused by the presence of three different absorption sheets located between the Sun and NGC 6124. The values of the internal dispersion of the polarization (ΔPV ~ 1.3 per cent) and of the colour excess (ΔE(B - V) ~ 0.29 mag) for the members of NGC 6124 seem to be compatible with the presence of an intracluster dust component. Only six stars exhibit some evidence of intrinsic polarization. Our work also shows that polarimetry provides an excellent tool to distinguish between member and non-member stars of a cluster. Based on observations obtained at Complejo Astronómico El Leoncito (CASLEO), operated under agreement between the CONICET and the National Universities of La Plata, Córdoba, and San Juan, Argentina. E-mail: cfeinstein@fcaglp.unlp.edu.ar (CF)

  13. Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and Their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm

    Science.gov (United States)

    Coffey, Victoria; Sazykin, Stan; Chandler, Michael O.; Hairston, Marc; Minow, Joseph I.; Anderson, Brian

    2017-01-01

    The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle. During this event, ionospheric F-region density measurements from the Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS) show dramatic depletions in the post-sunset (nighttime) local time sector at equatorial latitudes starting in the main phase of the storm and persisting on several subsequent orbits into the next day. Putting these low-latitude measurements in context with the global dynamics of the storm, we will present results from simulations and observations in our efforts to better understand the effects of this storm on the different regions of the coupled ionosphere-magnetosphere. The consequences of the magnetospheric penetration electric field and their role in the occurrence of these equatorial spread F observations will be investigated through the results of the SAMI3-RCM numerical model, a coupled ionosphere-magnetosphere model with self-consistent large-scale electrodynamics. Specifically, we will investigate the transient signatures of the interplanetary magnetic field component, Bz, and its role in driving the global convection electric field and ionospheric density redistribution. Lastly, measurements from the AMPERE Birkeland currents, DMSP drift velocities and the particle flux dropouts observed from the Magnetospheric Multiscale Mission (MMS) will be correlated with the FPMU density depletions and each other. Together these observations and simulation results will be assembled to provide each region's context to the global dynamics and time evolution of the storm.

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

    Science.gov (United States)

    Kappenman, J. G.

    2004-05-01

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

  15. X-ray and optical observations of four polars

    Science.gov (United States)

    Worpel, H.; Schwope, A. D.; Granzer, T.; Reinsch, K.; Schwarz, R.; Traulsen, I.

    2016-08-01

    Aims: We investigate the temporal and spectral behaviour of four polar cataclysmic variables from the infrared to X-ray regimes, refine our knowledge of the physical parameters of these systems at different accretion rates, and search for a possible excess of soft X-ray photons. Methods: We obtained and analysed four XMM-Newton X-ray observations of three of the sources, two of them discovered with the SDSS and one in the RASS. The X-ray data were complemented by optical photometric and spectroscopic observations and, for two sources, archival Swift observations. Results: SDSSJ032855.00+052254.2 was X-ray bright in two XMM-Newton and two Swift observations, and shows transitions from high and low accretion states on a timescale of a few months. The source shows no significant soft excess. We measured the magnetic field strength at the main accreting pole to be 39 MG and the inclination to be 45° ≤ i ≤ 77°, and we refined the long-term ephemeris. SDSSJ133309.20+143706.9 was X-ray faint. We measured a faint phase X-ray flux and plasma temperature for this source, which seems to spend almost all of its time accreting at a low level. Its inclination is less than about 76°. 1RXSJ173006.4+033813 was X-ray bright in the XMM-Newton observation. Its spectrum contained a modest soft blackbody component, not luminous enough to be considered a significant soft excess. We inferred a magnetic field strength at the main accreting pole of 20 to 25 MG, and that the inclination is less than 77° and probably less than 63°. V808 Aur, also known as CSS081231:J071126+440405, was X-ray faint in the Swift observation, but there is nonetheless strong evidence for bright and faint phases in X-rays and perhaps in UV. Residual X-ray flux from the faint phase is difficult to explain by thermal emission from the white dwarf surface, or by accretion onto the second pole. We present a revised distance estimate of 250 pc. Conclusions: The three systems we were able to study in detail

  16. Prompt Optical Observations of $\\gamma$-ray Bursts

    CERN Document Server

    Akerlof, Carl W; Barthelmy, S D; Bloch, J; Butterworth, P S; Casperson, D E; Cline, T; Fletcher, S; Frontera, F; Gisler, G; Heise, J; Hills, J; Hurley, K; Kehoe, R; Lee, B; Marshall, S; McKay, T; Pawl, A; Piro, L; Szymanski, J J; Wren, J; Akerlof, Carl; Balsano, Richard; Barthelmy, Scott; Bloch, Jeff; Butterworth, Paul; Casperson, Don; Cline, Tom; Fletcher, Sandra; Frontera, Fillippo; Gisler, Galen; Heise, John; Hills, Jack; Hurley, Kevin; Kehoe, Robert; Lee, Brian; Marshall, Stuart; Kay, Tim Mc; Pawl, Andrew; Piro, Luigi; Szymanski, John; Wren, Jim

    2000-01-01

    The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 square degree or better produced no detections. The earliest limiting sensitivity is m(ROTSE) > 13.1 at 10.85 seconds (5 second exposure) after the gamma-ray rise, and the best limit is m(ROTSE) > 16.0 at 62 minutes (897 second exposure). These are the most stringent limits obtained for GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission.

  17. EXCESS OPTICAL ENHANCEMENT OBSERVED WITH ARCONS FOR EARLY CRAB GIANT PULSES

    Energy Technology Data Exchange (ETDEWEB)

    Strader, M. J.; Mazin, B. A.; Spiro Jaeger, G. V.; Gwinn, C. R.; Meeker, S. R.; Szypryt, P.; Van Eyken, J. C.; Marsden, D.; Walter, A. B.; Ulbricht, G. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Johnson, M. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); O' Brien, K. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Stoughton, C. [Fermilab Center for Particle Astrophysics, Batavia, IL 60510 (United States); Bumble, B. [NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91125 (United States)

    2013-12-10

    We observe an extraordinary link in the Crab pulsar between the enhancement of an optical pulse and the timing of the corresponding giant radio pulse. At optical through infrared wavelengths, our observations use the high time resolution of ARray Camera for Optical to Near-IR Spectrophotometry, a unique superconducting energy-resolving photon-counting array at the Palomar 200 inch telescope. At radio wavelengths, we observe with the Robert C. Byrd Green Bank Telescope and the Green Bank Ultimate Pulsar Processing Instrument backend. We see an 11.3% ± 2.5% increase in peak optical flux for pulses that have an accompanying giant radio pulse arriving near the peak of the optical main pulse, in contrast to a 3.2% ± 0.5% increase when an accompanying giant radio pulse arrives soon after the optical peak. We also observe that the peak of the optical main pulse is 2.8% ± 0.8% enhanced when there is a giant radio pulse accompanying the optical interpulse. We observe no statistically significant spectral differences between optical pulses accompanied by and not accompanied by giant radio pulses. Our results extend previous observations of optical-radio correlation to the time and spectral domains. Our refined temporal correlation suggests that optical and radio emission are indeed causally linked, and the lack of spectral differences suggests that the same mechanism is responsible for all optical emission.

  18. Interplanetary magnetic field and geomagnetic Dst variations.

    Science.gov (United States)

    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.

  19. Evaluation of super intense geomagnetic storms and related structures of the interplanetary medium through the observation of cosmic rays of high energy surface; Analise de tempestades geomagneticas super intensas e de estruturas do meio interplanetario relacionadas, atraves da observacao de raios cosmicos de superficie de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Savian, Jairo Francisco; Schuch, Nelson J., E-mail: savian@lacesm.ufsm.br, E-mail: njschuch@lacesm.ufsm.br [Centro Regional Sul de Pesquisas Espaciais - CRSPE/INPE-MCT, Santa Maria, RS (Brazil); Silva, Marlos Rockenbach da; Lago, Alisson dal; Gonzalez, Walter Demetrio, E-mail: marlos@dge.inpe.br, E-mail: dallago@dge.inpe.br, E-mail: gonzalez@dge.inpe.br [Instituto Nacional de Pesquisas Espaciais - INPE-MCT, Sao Jose dos Campos, SP (Brazil); Munakata, Kazuoki [Physics Department, Shinshu University, Matsumoto (Japan)

    2005-04-15

    It is believed that the physical mechanism responsible for the transference of energy from the solar wind to the Earth magnetosphere is the reconnection between the interplanetary magnetic field and the terrestrial magnetic field (Tsurutani and Gonzalez, 1997). The necessary criterion for a intense geomagnetic storms to occur, Dst < -100nT, is the existence of a dawn-dusk interplanetary electric field larger than 5 mV/m, for a period larger than 3 hours. Cosmic rays have been studied as a natural phenomenon that can tell much about both Earth's environment in space and distant astrophysical processes (Jokipii, 2000). A solar disturbance propagating away from the Sun affects the pre-existing population of galactic cosmic rays in a number of ways. The most famous one is known as the 'Forbush decrease', which is a suppression of ground cosmic-ray counts observed during geomagnetic disturbances. The objective of this work is to study the response of the Southern Space Observatory ground Muon Telescope observations, installed in Sao Martinho da Serra, RS, Brazil, to 3 super intense geomagnetic storms, combining observation provided by L1 satellites and ground detectors. (author)

  20. Geomagnetic storm and equatorial spread-F

    Directory of Open Access Journals (Sweden)

    F. Becker-Guedes

    2004-09-01

    Full Text Available In August 2000, a new ionospheric sounding station was established at Sao Jose dos Campos (23.2° S, 45.9° W; dip latitude 17.6° S, Brazil, by the University of Vale do Paraiba (UNIVAP. Another ionospheric sounding station was established at Palmas (10.2° S, 48.2° W; dip latitude 5.5° S, Brazil, in April 2002, by UNIVAP in collaboration with the Lutheran University Center of Palmas (CEULP, Lutheran University of Brazil (ULBRA. Both the stations are equipped with digital ionosonde of the type known as Canadian Advanced Digital Ionosonde (CADI. In order to study the effects of geomagnetic storms on equatorial spread-F, we present and discuss three case studies, two from the ionospheric sounding observations at Sao Jose dos Campos (September and November 2000 and one from the simultaneous ionospheric sounding observations at Sao Jose dos Campos and Palmas (July 2003. Salient features from these ionospheric observations are presented and discussed in this paper. It has been observed that sometimes (e.g. 4-5 November 2000 the geomagnetic storm acts as an inhibitor (high strong spread-F season, whereas at other times (e.g. 11-12 July 2003 they act as an initiator (low strong spread-F season, possibly due to corresponding changes in the quiet and disturbed drift patterns during different seasons.

  1. Surface Material Characterization from Multi-band Optical Observations

    Science.gov (United States)

    Hall, D.

    2010-09-01

    Ground-based optical and radar sites routinely acquire resolved images of satellites. These resolved images provide the means to construct accurate wire-frame models of the observed body, as well as an understanding of its orientation as a function of time. Unfortunately, because such images are typically acquired in a single spectral band, they provide little information on the types of materials covering the satellite's various surfaces. Detailed surface material characterization generally requires spectrometric and/or multi-band photometric measurements. Fortunately, many instruments provide such multi-band information (e.g., spectrographs and multi-channel photometers). However, these sensors often measure the brightness of the entire satellite, with no spatial resolution at all. Because such whole-body measurements represent a summation of contributions from many reflecting surfaces, an ―un-mixing‖ or inversion process must be employed to determine the materials covering each of the satellite's individual sub-components. The first section of this paper describes the inversion theory required to retrieve satellite surface material properties from temporal sequences of whole-body multi-band brightness measurements. The inversion requires the following as input: 1) a set of multi-band measurements of a satellite's reflected-sunlight brightness, 2) the satellite's wire-frame model, including each major component capable of reflecting sunlight, 3) the satellite's attitude, specifying the body’s orientation at the time of each multi-band measurement, and 4) a database of bi-directional reflection distribution functions for a set of candidate surface materials. As output, the inversion process yields estimates of the fraction of each major satellite component covered by each candidate material. The second section of the paper describes several tests of the method by applying it to simulated multi-band observations of a cubical satellite with different materials

  2. The Egyptian geomagnetic reference field to the Epoch, 2010.0

    Science.gov (United States)

    Deebes, H. A.; Abd Elaal, E. M.; Arafa, T.; Lethy, A.; El Emam, A.; Ghamry, E.; Odah, H.

    2017-06-01

    The present work is a compilation of two tasks within the frame of the project ;Geomagnetic Survey & Detailed Geomagnetic Measurements within the Egyptian Territory; funded by the ;Science and Technology Development Fund agency (STDF);. The National Research Institute of Astronomy and Geophysics (NRIAG), has conducted a new extensive land geomagnetic survey that covers the whole Egyptian territory. The field measurements have been done at 3212 points along all the asphalted roads, defined tracks, and ill-defined tracks in Egypt; with total length of 11,586 km. In the present work, the measurements cover for the first time new areas as: the southern eastern borders of Egypt including Halayeb and Shlatin, the Quattara depresion in the western desert, and the new roads between Farafra and Baharia oasis. Also marine geomagnetic survey have been applied for the first time in Naser lake. Misallat and Abu-Simble geomagnetic observatories have been used to reduce the field data to the Epoch 2010. During the field measurements, whenever possible, the old stations occupied by the previous observers have been re-occupied to determine the secular variations at these points. The geomagnetic anomaly maps, the normal geomagnetic field maps with their corresponding secular variation maps, the normal geomagnetic field equations of the geomagnetic elements (EGRF) and their corresponding secular variations equations, are outlined. The anomalous sites, as discovered from the anomaly maps are, only, mentioned. In addition, a correlation between the International Geomagnetic Reference Field (IGRF) 2010.0 and the Egyptian Geomagnetic Reference Field (EGRF) 2010 is indicated.

  3. Report of geomagnetic pulsation indices for space weather applications

    Science.gov (United States)

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

    2013-01-01

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

  4. Gravitational and geomagnetic tidal source of earthquake triggering

    Science.gov (United States)

    Palumbo, A.

    1989-12-01

    A relationship is presently established between large earthquakes and the earth's tides and external geomagnetic fields, in conjunction with a triggering mechanism having its bases in the large solar and lunar variations observed during a number of the shocks examined. A majority of these shocks are noted to be located within a latitude-belt which coincides with the intensity maximum of ionospheric currents. A local magnetostriction process in the rocks appears to be the triggering mechanism. The large number of earthquakes occurring during maximum solar activity may be related to the enhanced geomagnetic triggering effect of higher sunspot numbers.

  5. Mantle superplumes induce geomagnetic superchrons

    Directory of Open Access Journals (Sweden)

    Peter eOlson

    2015-07-01

    Full Text Available We use polarity reversal systematics from numerical dynamos to quantify the hypothesis that the modulation of geomagnetic reversal frequency, including geomagnetic superchrons, results from changes in core heat flux related to growth and collapse of lower mantle superplumes. We parameterize the reversal frequency sensitivity from numerical dynamos in terms of average core heat flux normalized by the difference between the present-day core heat flux and the core heat flux at geomagnetic superchron onset. A low-order polynomial fit to the 0-300 Ma Geomagnetic Polarity Time Scale (GPTS reveals that a decrease in core heat flux relative to present-day of approximately 30% can account for the Cretaceous Normal Polarity and Kiaman Reverse Polarity Superchrons, whereas the hyper-reversing periods in the Jurassic require a core heat flux equal to or higher than present-day. Possible links between GPTS transitions, large igneous provinces (LIPs, and the two lower mantle superplumes are explored. Lower mantle superplume growth and collapse induce GPTS transitions by increasing and decreasing core heat flux, respectively. Age clusters of major LIPs postdate transitions from hyper-reversing to superchron geodynamo states by 30-60 Myr, suggesting that superchron onset may be contemporaneous with LIP-forming instabilities produced during collapses of lower mantle superplumes.

  6. Solar dynamo and geomagnetic activity

    CERN Document Server

    Georgieva, Katya

    2010-01-01

    The correlation between geomagnetic activity and the sunspot number in the 11-year solar cycle exhibits long-term variations due to the varying time lag between the sunspot-related and non-sunspot related geomagnetic activity, and the varying relative amplitude of the respective geomagnetic activity peaks. As the sunspot-related and non-sunspot related geomagnetic activity are caused by different solar agents, related to the solar toroidal and poloidal fields, respectively, we use their variations to derive the parameters of the solar dynamo transforming the poloidal field into toroidal field and back. We find that in the last 12 cycles the solar surface meridional circulation varied between 5 and 20 m/s (averaged over latitude and over the sunspot cycle), the deep circulation varied between 2.5 and 5.5 m/s, and the diffusivity in the whole of the convection zone was ~10**12 m2/s. In the last 12 cycles solar dynamo has been operating in moderately diffusion dominated regime in the bulk of the convection zone....

  7. The geomagnetic field gradient tensor

    DEFF Research Database (Denmark)

    Kotsiaros, Stavros; Olsen, Nils

    2012-01-01

    We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independe...... of the small-scale structure of the Earth’s lithospheric field....

  8. A New Theory of Geomagnetism

    OpenAIRE

    Sidharth, B. G.

    1999-01-01

    It is pointed out, that in the light of recent results on the semionic or anomalous behaviour of electrons below the Fermi temperature, the solid core of the earth which has been ignored so far, would contribute significantly to Geomagnetism and help explain the puzzling magnetic reversals.

  9. Apparatus for observing a sample with a particle beam and an optical microscope

    NARCIS (Netherlands)

    2010-01-01

    An apparatus for observing a sample (1) with a TEM column and an optical high resolution scanning microscope (10). The sample position when observing the sample with the TEM column differs from the sample position when observing the sample with the optical microscope in that in the latter case the

  10. Apparatus for observing a sample with a particle beam and an optical microscope

    NARCIS (Netherlands)

    2010-01-01

    An apparatus for observing a sample (1) with a TEM column and an optical high resolution scanning microscope (10). The sample position when observing the sample with the TEM column differs from the sample position when observing the sample with the optical microscope in that in the latter case the s

  11. Keck Adaptive Optics Observations of Neptune's Ring and Satellite Keck Adaptive Optics Observations of Neptune's Ring and Satellite System

    Science.gov (United States)

    de Pater, I.; Gibbard, S.; Martin, S.; Marchis, F.; Roe, H. G.; Macintosh, B.

    2003-05-01

    We observed Neptune, its satellites and ring system on UT 27 and 28 July 2002, with NIRC2 on the 10-m Keck II telescope at 2.2 micron. The total field of view was 10". Each image was integrated for 1 minute; on the first day we had a total of 18 frames, and 33 images on the second day, each spread out over a time interval of 1-2 hours. The complete Adams and Le Verrier rings are visible on each day, after combining all images. In the regions away from the ring arcs, we find that the Le Verrier ring is brighter (up to 20-40%) than the Adams ring. The ring arcs are readily apparent in combinations of the data that take into account Keplerian motion. The ring arc positions are in close agreement with Nicholson et al's (1995) result, as in HST/NICMOS images (Dumas et al. 2002). The Egalite ring has broadened even more since observed with HST/NICMOS in 1998, and is clearly the brightest ring arc. Liberte has decreased in intensity since Voyager and NICMOS. Courage was extremely faint in our images. The satellites Proteus, Larissa, Galatea and Despina are easily seen on individual frames. Thalassa is detected after properly shifting/rotating and adding several frames. This is the first time since the Voyager flybys that Thalassa is detected. Preliminary astrometric measurements suggest the satellites Larissa and Galathea, relative to Proteus, to be off from their nominal (JPL Horizons) positions by 0.3", and Despina by 0.1". Recent results indicate that Proteus is offset by 0.1" compared to Triton (Martins et al. 2003). Preliminary I/F values are 0.06 for Proteus, 0.045 for Larissa and Galatea, and 0.03 for Despina and Thalassa. These observations were supported by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under cooperative agreement No. AST-9876783

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

    Science.gov (United States)

    Badruddin; Kumar, Anand

    2015-04-01

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

  13. Behavior of Plasma and Field Parameters and their Relationship with Geomagnetic Indices during Intense Geomagnetic Storms of Solar Cycle 23

    CERN Document Server

    Joshi, Navin Chandra; Pande, Seema; Pande, Bimal; Pandey, Kavita

    2010-01-01

    A correlative study between the geomagnetic indices and the peak values of various plasma and field parameters during rising, maximum and decay phases as well as during complete solar cycle 23 have been presented. We have also presented the lag/lead analysis between the maximum of Dst and peak values of plasma and field parameters and found that peak values of lag/lead time lies in the +/-10 hr interval. Three geomagnetic storms (GMSs) and associated solar sources observed during these phases of this solar cycle have also been studied and found that GMSs are associated with large flares and halo CMEs.

  14. Can the tardigrade Hypsibius dujardini survive in the absence of the geomagnetic field?

    Science.gov (United States)

    Erdmann, Weronika; Idzikowski, Bogdan; Kowalski, Wojciech; Szymański, Bogdan; Kosicki, Jakub Z; Kaczmarek, Łukasz

    2017-01-01

    Earth's geomagnetic field has undergone critical changes in the past. Studies on the influence of the magnetic field on Earth's organisms are crucial for the understanding of evolution of life on Earth and astrobiological considerations. Numerous studies conducted both on plants and animals confirmed the significant influence of the geomagnetic field on the metabolism of living organisms. Water bears (Tardigrada), which are a mong the most resistant animals due to their cryptobiotic abilities, show significant resistance to a number of environmental stressors, but the influence of the geomagnetic field on their fitness has not been addressed before. In our studies, we used eutardigrade Hypsibius dujardini to analyse whether isolation from the geomagnetic field had an effect on mortality. We found that Hypsibius dujardini specimens demonstrated relatively high mortality during anhydrobiosis, also in control groups exposed to the normal geomagnetic field. Moreover, similar mortality was observed in anhydrobiotic specimens isolated from the geomagnetic field. However, a significant difference was noted between tardigrade survival and the moment of their isolation from the geomagnetic field. In particular, tardigrade mortality substantially increased in absence of a magnetic field during the process of entering anhydrobiosis and returning to active life. Our results suggest that these processes rely on complex metabolic processes that are critically influenced by the geomagnetic field.

  15. Solar Wind Charge Exchange During Geomagnetic Storms

    Science.gov (United States)

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

    2012-01-01

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

  16. Geomagnetic control of polar mesosphere summer echoes

    Directory of Open Access Journals (Sweden)

    J. Bremer

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

    Keywords: Ionosphere (auroral ionosphere - Magnetospheric physics (energetic particles, precipitating - Radio science (remote sensing

  17. Kepler Observations of Rapid Optical Variability in Active Galactic Nuclei

    CERN Document Server

    Mushotzky, Richard F; Baumgartner, Wayne H; Gandhi, Poshak

    2011-01-01

    Over three quarters in 2010-2011, Kepler monitored optical emission from four active galactic nuclei (AGN) with ~30 min sampling, >90% duty cycle, and <~0.1% repeatability. These data determined the AGN optical fluctuation power spectral density functions (PSDs) over a wide range in temporal frequency. Fits to these PSDs yielded power law slopes of -2.6 to -3.3, much steeper than typically seen in the X-rays. We find evidence that individual AGN exhibit intrinsically different PSD slopes. The steep PSD fits are a challenge to recent AGN variability models but seem consistent with first order MRI theoretical calculations of accretion disk fluctuations.

  18. Observation and simulation of an optically driven micromotor

    Science.gov (United States)

    Metzger, N. K.; Mazilu, M.; Kelemen, L.; Ormos, P.; Dholakia, K.

    2011-04-01

    In the realm of low Reynolds number flow there is a need to find methods to pump, move and mix minute amounts of analyte. Interestingly, micro-devices performing such actuation can be initiated by means of the light-matter interaction. Light induced forces and torques are exerted on such micro-objects, which are then driven by the optical gradient or scattering force. Here, different driving geometries can be realized to harness the light induced force. For example, the scattering force enables micro-gears to be operated in a tangential setup where the micromotor rotors are in line with an optical waveguide. The operational geometry we investigate has the advantage that it reduces the complexity of the driving of such a device in a microfluidic environment by delivering the actuating light by means of a waveguide or fiber optic. In this paper we explore the case of a micromotor being driven by a fiber optically delivered light beam. We experimentally investigate how the driving light interacts with and diffracts from the motor, utilizing two-photon imaging. The micromotor rotation rate dependence on the light field parameters is explored. Additionally, a theoretical model based on the paraxial approximation is used to simulate the torque and predict the rotation rate of such a device and compare it with experiment. The results presented show that our model can be used to optimize the micromotor performance and some example motor designs are evaluated.

  19. A remarkable recurrent nova in M31 - The optical observations

    CERN Document Server

    Darnley, M J; Bode, M F; Henze, M; Ness, J -U; Shafter, A W; Hornoch, K; Votruba, V

    2014-01-01

    Context. In late November 2013 a fourth outburst in five years of the M31 recurrent nova M31N 2008-12a was announced. Aims. In this Letter we address the optical lightcurve and progenitor system of M31N 2008-12a. Methods. Optical imaging data of the 2013 outburst from the Liverpool Telescope, La Palma, and Danish 1.54m Telescope, La Silla, and archival Hubble Space Telescope near-IR, optical and near-UV data are astrometrically and photometrically analysed. Results. Photometry of the 2013 outburst, combined with the previous three, enabled construction of a template lightcurve of a very fast nova (t2 (V) ~4 days). The archival data allowed recovery of the progenitor system in optical and near-UV data, indicating a red-giant secondary with bright accretion disk, or alternatively a system with a sub-giant secondary but dominated by a disk. Conclusions. The outbursts of M31N 2008-12a, plus a number of historic X-ray detections, indicate a unique system with a recurrence timescale of ~1 year. This implies the pre...

  20. Extreme Geomagnetic Storms - 1868 - 2010

    Science.gov (United States)

    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

  1. Cosmic rays, geomagnetic field and climate changes

    Science.gov (United States)

    Shea, M.; Smart, D.

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

  2. Research on Historical Records of Geomagnetic Storms

    Science.gov (United States)

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

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

  3. Geomagnetic storm effects on GPS based navigation

    Directory of Open Access Journals (Sweden)

    P. V. S. Rama Rao

    2009-05-01

    Full Text Available The energetic events on the sun, solar wind and subsequent effects on the Earth's geomagnetic field and upper atmosphere (ionosphere comprise space weather. Modern navigation systems that use radio-wave signals, reflecting from or propagating through the ionosphere as a means of determining range or distance, are vulnerable to a variety of effects that can degrade the performance of the navigational systems. In particular, the Global Positioning System (GPS that uses a constellation of earth orbiting satellites are affected due to the space weather phenomena.

    Studies made during two successive geomagnetic storms that occurred during the period from 8 to 12 November 2004, have clearly revealed the adverse affects on the GPS range delay as inferred from the Total Electron Content (TEC measurements made from a chain of seven dual frequency GPS receivers installed in the Indian sector. Significant increases in TEC at the Equatorial Ionization anomaly crest region are observed, resulting in increased range delay during the periods of the storm activity. Further, the storm time rapid changes occurring in TEC resulted in a number of phase slips in the GPS signal compared to those on quiet days. These phase slips often result in the loss of lock of the GPS receivers, similar to those that occur during strong(>10 dB L-band scintillation events, adversely affecting the GPS based navigation.

  4. KEPLER OBSERVATIONS OF RAPID OPTICAL VARIABILITY IN ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Mushotzky, R. F.; Edelson, R. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Baumgartner, W. [Laboratory for High Energy Astrophysics, NASA/GSFC, Code 662, Greenbelt, MD 20771 (United States); Gandhi, P., E-mail: richard@astro.umd.edu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

    2011-12-10

    Over three quarters in 2010-2011, Kepler monitored optical emission from four active galactic nuclei (AGNs) with {approx}30 minute sampling, >90% duty cycle, and {approx}<0.1% repeatability. These data determined the AGN optical fluctuation power spectral density (PSD) functions over a wide range in temporal frequency. Fits to these PSDs yielded power-law slopes of -2.6 to -3.3, much steeper than typically seen in the X-rays. We find evidence that individual AGNs exhibit intrinsically different PSD slopes. The steep PSD fits are a challenge to recent AGN variability models but seem consistent with first-order magnetorotational instability theoretical calculations of accretion disk fluctuations.

  5. The UFFO slewing mirror telescope for early optical observation from gamma ray bursts

    DEFF Research Database (Denmark)

    NAM, JIWOO; AHMAD, S.; AHN, K.;

    2013-01-01

    While some space born observatories, such as SWIFT and FERMI, have been operating, early observation of optical after grow of GRBs is still remained as an unexplored region. The Ultra-Fast Flash Observatory (UFFO) project is a space observatory for optical follow-ups of GRBs, aiming to explore...... the first 60 seconds of GRBs optical emission. Using fast moving mirrors to redirect our optical path rather than slewing the entire spacecraft, UFFO is utilized to catch early optical emissions from GRB within 1 sec. We have developed the UFFO Pathfinder Telescope which is going to be on board...

  6. The Uffo Slewing Mirror Telescope for Early Optical Observation from Gamma Ray Bursts

    DEFF Research Database (Denmark)

    Nam, Jiwoo; Ahmad, S.; Ahn, K.;

    2013-01-01

    While some space born observatories, such as SWIFT and FERMI, have been operating, early observation of optical after grow of GRBs is still remained as an unexplored region. The Ultra-Fast Flash Observatory (UFFO) project is a space observatory for optical follow-ups of GRBs, aiming to explore...... the first 60 seconds of GRBs optical emission. Using fast moving mirrors to redirect our optical path rather than slewing the entire spacecraft, UFFO is utilized to catch early optical emissions from GRB within 1 sec. We have developed the UFFO Pathfinder Telescope which is going to be on board...

  7. Heart attacks and geomagnetic activity.

    Science.gov (United States)

    Knox, E G; Armstrong, E; Lancashire, R; Wall, M; Haynes, R

    1979-10-18

    Malin and Srivastava reported a remarkable correlation between daily variations in the geomagnetic field strength and daily admissions to the cardio-thoracic wards of hospitals in Hyderabad and Secunderabad, for cardiac emergencies, during 1967--72. We have now carried out a similar enquiry in the West Midlands region of the UK for the years 1969--70, but were unable to confirm the Indian results.

  8. Entry Dispersion Analysis for the Hayabusa Spacecraft using Ground Based Optical Observation

    CERN Document Server

    Yamaguchi, T; Yagi, M; Tholen, D J

    2011-01-01

    Hayabusa asteroid explorer successfully released the sample capsule to Australia on June 13, 2010. Since the Earth reentry phase of sample return was critical, many backup plans for predicting the landing location were prepared. This paper investigates the reentry dispersion using ground based optical observation as a backup observation for radiometric observation. Several scenarios are calculated and compared for the reentry phase of the Hayabusa to evaluate the navigation accuracy of the ground-based observation. The optical observation doesn't require any active reaction from a spacecraft, thus these results show that optical observations could be a steady backup strategy even if a spacecraft had some trouble. We also evaluate the landing dispersion of the Hayabusa only with the optical observation.

  9. Optical kinematics in the Cygnus Loop. I - Observations

    Science.gov (United States)

    Greidanus, H.; Strom, R. G.

    1991-07-01

    The small-scale radial-velocity structure of optical filaments in the Cygnus Loop supernova remnant was mapped in the H-alpha and forbidden O III 5007-A emission lines with a resolution of 6 arcsec spatially and 24 km/s in radial velocity. The imaging Fabry-Perot interferometer Taurus was used, and some aspects of velocity calibration are discussed. The calibrated data, in the form of 3D matrices of intensity as a function of sky position and radial velocity, are presented here as position-velocity cross-cuts, and as total intensity and radial velocity maps.

  10. Observation of nitrogen vacancy photoluminescence from an optically levitated nanodiamond

    CERN Document Server

    Neukirch, Levi P; Quidant, Romain; Novotny, Lukas; Vamivakas, A Nick

    2013-01-01

    We present the first evidence of nitrogen vacancy (NV) photoluminescence from a nanodiamond suspended in a free-space optical dipole trap at atmospheric pressure. The photoluminescence rates are shown to decrease with increasing trap laser power, but are inconsistent with a thermal quenching process. For a continuous-wave trap, the neutral charge state (NV$^0$) appears to be suppressed. Chopping the trap laser yields higher total count rates and results in a mixture of both NV$^0$ and the negative charge state (NV$^-$).

  11. Early-Time Observations of the GRB 050319 Optical Transient

    CERN Document Server

    Quimby, R M; Yost, S A; Aharonian, F; Akerlof, C W; Alatalo, K; Ashley, M C B; Goegues, E; Guever, T; Horns, D; Kehoe, R L; Kiziloglu, U; McKay, T A; Oezel, M; Phillips, A; Schaefer, B E; Smith, D A; Swan, H F; Vestrand, W T; Wheeler, J C; Wren, J; Kiziloglu, Ue.

    2006-01-01

    We present the unfiltered ROTSE-III light curve of the optical transient associated with GRB 050319 beginning 4 s after the cessation of gamma-ray activity. We fit a power-law function to the data using the revised trigger time given by Chincarini et al. (2005), and a smoothly broken power-law to the data using the original trigger disseminated through the GCN notices. Including the RAPTOR data from Wozniak et al. (2005), the best fit power-law indices are alpha=-0.854 (+/- 0.014) for the single power-law and alpha_1=-0.364 (+/- 0.020), alpha_2= -0.881 (+/- 0.030), with a break at t_b = 418 (+/- 30) s for the smoothly broken fit. We discuss the fit results with emphasis placed on the importance of knowing the true start time of the optical transient for this multi-peaked burst. As Swift continues to provide prompt GRB locations, it becomes more important to answer the question, "when does the afterglow begin" to correctly interpret the light curves.

  12. The Causes of Geomagnetic Storms During Solar Maximum

    Science.gov (United States)

    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. Observation of optical-fiber Kerr nonlinearity at the single-photon level

    CERN Document Server

    Matsuda, Nobuyuki; Mitsumori, Yasuyoshi; Kosaka, Hideo; Edamatsu, Keiichi; 10.1038/nphoton.2008.292

    2012-01-01

    Optical fibers have been enabling numerous distinguished applications involving the operation and generation of light, such as soliton transmission, light amplification, all-optical switching and supercontinuum generation. The active function of optical fibers in the quantum regime is expected to be applicable to ultralow-power all-optical signal processing and quantum information processing. Here we demonstrate the first experimental observation of optical nonlinearity at the single-photon level in an optical fiber. Taking advantage of large nonlinearity and managed dispersion of a photonic crystal fiber, we have successfully measured very small (10^(-7) ~ 10^(-8)) conditional phase shifts induced by weak coherent pulses that contain one or less than one photon per pulse on average. In spite of its tininess, the phase shift was measurable using much (~10^6 times) stronger coherent probe pulses than the pump pulses. We discuss the feasibility of quantum information processing using optical fibers, taking into...

  14. "Double low-points" anomaly in daily variation of vertical component of geomagnetic field before the MS8.0 Wenchuan earthquake

    Institute of Scientific and Technical Information of China (English)

    Jiuchang Hu; Wei Liu; Minrui Guo; Hua Zheng

    2009-01-01

    The "double low-points" anomaly in daily variation of vertical geomagnetic component was observed on May 9, 2008 at 13 geomagnetic observatories belonging to the geomagnetic observatory network center of China Earthquake Administration. These observatories distribute roughly on three belts with the intersection in western Sichuan. On May 12, three days after the anomaly appearance, the great MS8.0 Wenchuan earthquake occurred. The "double low-points" anomaly in daily variation of vertical geomagnetic component is an anomalous phenomenon of regional geomagnetism, which does exist objectively. The possible cause is the change of extrinsic eddy current system resulting in geomagnetic daily quiet variation (Sq), or the delay of several hours between the intrinsic and the extrinsic eddy current systems. The relationship between the "double low-points" anomaly of daily geomagnetic variation and the earthquake reveals that the former possibly reflects the accelera-tive alteration of earthquake gestation in the deep Earth.

  15. Sources of the Geomagnetic Field and theModern Data That Enable Their Investigation

    DEFF Research Database (Denmark)

    Olsen, Nils; Hulot, Gauthier; Sabaka, Terence J.

    2010-01-01

    Abstract The geomagnetic field one canmeasure at the Earth’s surface or on board satellites is the sumof contributions frommany different sources.These sources have different physical origins and can be found both below (in the form of electrical currents and magnetized material) and above (only...... sets are available and analyzed in an adequate way, to produce the so-called geomagnetic field models.Here a general overview of the various sources that contribute to the observed geomagnetic field, and of the modern data that enable their investigation via such procedures is provided....

  16. Optical rebrightening of the blazar AO 0235+16 observed by the GASP

    Science.gov (United States)

    Villata, M.; Raiteri, C. M.; Larionov, V. M.; Konstantinova, T. S.; Kopatskaya, E. N.; Larionova, L.; Chen, W. P.; Koptelova, E.; Nilsson, K.; Pasanen, M.; Ligustri, R.; Böttcher, M.; Roustazadeh, P.; Diltz, C.

    2008-10-01

    With reference to ATels #1724, #1735, #1744, #1784 on the high radio-to-optical and gamma-ray activity of the blazar AO 0235+16, the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reports on the recent observation of a strong optical rebrightening of the source. After the optical peak of R ~ 14.2 reached on September 24.1, 2008, the brightness rapidly decreased by 2 mags in the following 10 days.

  17. Observations of the Prompt Optical Emission of GRB 160625B with Mini-MegaTORTORA

    Science.gov (United States)

    Karpov, S.; Beskin, G.; Biryukov, A.; Bondar, S.; Ivanov, E.; Katkova, E.; Orekhova, N.; Perkov, A.; Sasyuk, V.

    2017-06-01

    Here we report our observations of bright optical flash coincident with Fermi GRB160625B using Mini-MegaTORTORA wide-field monitoring system. The prompt optical emission is correlated with gamma one and lags behind it for about 3 seconds, that suggests that optical and gamma emission are formed in different regions of the burst. The multiwavelength properties of this burst are very similar to ones of Naked-Eye Burst, GRB080319B, we detected earlier with TORTORA camera.

  18. Simultaneous optical and radio observations of flare stars in the Pleiades

    Energy Technology Data Exchange (ETDEWEB)

    Tovmassian, H.M.; Haro, G.; Webber, J.C.; Swenson, G.W. Jr.; Yang, K.S.; Yoss, K.M.; Deming, D.; Green, R.F.

    1974-01-01

    Simultaneous optical (at Tonantzintla, Palomar, and Prairie Observatories) and radio (at the Vermilion River and Owens Valley Radio Observatories) observations of the flare stars in the Pleiades cluster were made from October 1 to 6, 1972. Eleven optical flare-ups were detected. One large flare-up (greater than 8/sup m/ in U) was accompanied by radio flare at 170 MHz. The ratio of optical to radio energy output of this flare is about 6 . 10/sup 2/.

  19. Observations of the Geometry of Horizon-Based Optical Navigation

    Science.gov (United States)

    Christian, John; Robinson, Shane

    2016-01-01

    NASA's Orion Project has sparked a renewed interest in horizon-based optical navigation(OPNAV) techniques for spacecraft in the Earth-Moon system. Some approaches have begun to explore the geometry of horizon-based OPNAV and exploit the fact that it is a conic section problem. Therefore, the present paper focuses more deeply on understanding and leveraging the various geometric interpretations of horizon-based OPNAV. These results provide valuable insight into the fundamental workings of OPNAV solution methods, their convergence properties, and associated estimate covariance. Most importantly, the geometry and transformations uncovered in this paper lead to a simple and non-iterative solution to the generic horizon-based OPNAV problem. This represents a significant theoretical advancement over existing methods. Thus, we find that a clear understanding of geometric relationships is central to the prudent design, use, and operation of horizon-based OPNAV techniques.

  20. Coordinated optical and ultraviolet observations of DH Leo

    Science.gov (United States)

    Newmark, Jeffrey S.; Buzasi, Derek L.; Huenemoerder, David P.; Ramsey, Lawrence W.; Barden, Samuel C.

    1990-01-01

    Results are reported from contemporaneous KPNO optical spectroscopy, IUE UV spectroscopy, and KPNO R photometry of the DH Leo triple system in spring 1987. The data are presented in tables, graphs, and spectral phase images and discussed in detail. The H-alpha, H-beta, H-gamma, H-delta, and Ca II H and IRT lines are found to have excess emission, and the phase modulation in H-alpha, H-beta, and Ca II is well correlated with the photometric modulation. This result is attributed to the combination of (1) a small amount of global chromospheric emission and (2) emission from plagelike regions associated with cool starspots. The (H-alpha)/(H-beta) ratio is found to be significantly lower than that in longer-period RS CVn systems.

  1. Adaptive Optics at Optical Wavelengths: Test Observations of Kyoto 3DII Connected to Subaru Telescope AO188

    Science.gov (United States)

    Matsubayashi, K.; Sugai, H.; Shimono, A.; Akita, A.; Hattori, T.; Hayano, Y.; Minowa, Y.; Takeyama, N.

    2016-09-01

    Adaptive optics (AO) enables us to observe objects with high spatial resolution, which is important in most astrophysical observations. Most AO systems are operational at near-infrared wavelengths but not in the optical range, because optical observations require a much higher performance to obtain the same Strehl ratio as near-infrared observations. Therefore, to enable AO-assisted observations at optical wavelengths, we connected the Kyoto Tridimensional Spectrograph II (Kyoto 3DII), which can perform integral field spectroscopy, to the second generation AO system of the Subaru Telescope (AO188). We developed a new beam-splitter that reflects light below 594 nm for the wavefront sensors of AO188 and transmits above 644 nm for Kyoto 3DII. We also developed a Kyoto 3DII mount at the Nasmyth focus of the Subaru Telescope. In test observations, the spatial resolution of the combined AO188-Kyoto 3DII was higher than that in natural seeing conditions, even at 6500 Å. The full width at half maximum of an undersampled (1.5 spaxels) bright guide star (7.0 mag in the V-band) was 0.″12.

  2. Delays of optical bursts in simultaneous optical and X-ray observations of MXB 1636-53

    Science.gov (United States)

    Matsuoka, M.; Mitsuda, K.; Ohashi, T.; Inoue, H.; Koyama, K.; Makino, F.; Makishima, K.; Murakami, T.; Oda, M.; Ogawara, Y.

    1984-01-01

    Observations of simultaneous optical and X-ray bursts from 4U/MXB 1636-53 were made using the Hakucho burst monitor system and optical telescopes at the European Southern Observatory during 1979 and 1980. The six best cases among the 10 coinciding observations are analyzed in terms of a model in which the optical emission is the result of reprocessing of X-rays (through blackbody heating). From this analysis, the temperature (spatially averaged) and size of a reprocessor, and the smearing and delay of the optical bursts are obtained. For the maximum temperatures of the optical reprocessor, the values differ from burst to burst, ranging from about 3 x 10 to the 4th to about 10 to the 5th K. The present analysis suggests that the size of the reprocessor varies by a factor of a few. For the smearing of the optical bursts an upper limit of a few seconds is derived. The most important result of this analysis is that the delay times are not the same for all bursts. The possible constraints which these results put on a low-mass binary model of this burst source are discussed.

  3. Observations of regional and local variability in the optical properties of maritime clouds

    Energy Technology Data Exchange (ETDEWEB)

    White, A.B. [Univ. of Colorado at Boulder/National Oceanic and Atmospheric Administration, Boulder, CO (United States); Fairall, C.W. [Environmental Technology Lab., Boulder, CO (United States)

    1996-04-01

    White and Fairall (1995) calculated the optical properties of the marine boundary layer (MBL) clouds observed during the Atlantic Stratocumulus Transition Experiment (ASTEX) and compared their results with the results obtained by Fairall et al. for the MBL clouds observed during the First International Satellite Climatology Program (ISSCP) Regional Experiment (FIRE). They found a factor of two difference in the optical depth versus liquid water relationship that applies to the clouds observed in each case. In the present study, we present evidence to support this difference. We also investigate the local variability exhibited in the ASTEX optical properties using measurements of the boundary layer aerosol concentration.

  4. The Optical-Near-IR Spectrum of the M87 Jet From HST Observations

    CERN Document Server

    Perlman, E S; Sparks, W; Macchetto, D; Leahy, J P; Perlman, Eric S.; Biretta, John; Sparks, William; Macchetto, Duccio

    2000-01-01

    We present 1998 HST observations of M87 which yield the first single-epoch optical and radio-optical spectral index images of the jet at $0.15''$ resolution. We find $ \\approx 0.67$, comparable to previous measurements, and $ \\approx 0.9$ ($F_\

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

    Science.gov (United States)

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

    2017-01-01

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

  6. Geomagnetic properties of Proxima Centauri b analogues

    CERN Document Server

    Zuluaga, Jorge I

    2016-01-01

    The recent discovery of a planet around the closest star, Proxima Centauri, could represent a quantum leap on the testability of models in exoplanet sciences. Unlike any other discovered exoplanet, models of planetary processes in Proxima b could be contrasted against near future telescopic observations and far future in-situ measurements. In this paper we study the geomagnetic properties of Proxima b analogues, namely, solid planets with masses close but larger than Earth's mass, periods of rotation of several days and habitable surface conditions. Assuming different planetary masses, bulk compositions and periods of rotations, we calculate for each planetary analogue its radius, heat flux, time of inner core formation, dynamo lifetime and minimum dipole magnetic moment. We find that most ($\\gtrsim$70\\%) Proxima b analogues develop intrinsic dynamos that last at least 3 Gyr, although only half of them are older than the present age of the host star ($4-6$ Gyr). Relying in our planetary evolution models, we p...

  7. Estimation of cold plasma outflow during geomagnetic storms

    CERN Document Server

    Haaland, S; André, M; Maes, L; Baddeley, L; Barakat, A; Chappell, R; Eccles, V; Johnsen, C; Lybekk, B; Li, K; Pedersen, A; Schunk, R; Welling, D

    2016-01-01

    Low-energy ions of ionospheric origin constitute a significant contributor to the magnetospheric plasma population. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and typically in regions of space where spacecraft attain a positive charge due to solar illumination. Cold ions are therefore shielded from the satellite particle detectors. Furthermore, spacecraft can only cover key regions of ion outflow during segments of their orbit, so additional complications arise if continuous longtime observations, such as during a geomagnetic storm, are needed. In this paper we suggest a new approach, based on a combination of synoptic observations and a novel technique to estimate the flux and total outflow during the various phases of geomagnetic storms. Our results indicate large variations in both outflow rates and transport throughout the storm. Prior to the storm main phase, outflow rates are moderate, and the cold ions are mainly emanating from moderately sized ...

  8. Geomagnetic Storms and their Influence on the Human Brain Functional State

    Directory of Open Access Journals (Sweden)

    Elchin S. Babayev

    2005-01-01

    Full Text Available An investigation of the influence of geomagnetic storms of various intensities on healthy adults' human brain activity and its functional state was conducted. Results of electroencephalogram (EEG investigations were used as the most objective method reflecting functional state of the human brain. Studies on the influence of geomagnetic storms on the human brain functional state of healthy adult women patients (permanent group in states of relaxation, photo-stimulation and hyper-ventilation have revealed a negative influence of severe geomagnetic storms on functional state of the human brain. As a rule, during periods of strong geomagnetic disturbances, indisposition, weakness and presence of indistinct localized headaches were recorded for majority of patients. Complex of nonspecific shifts on EEG reflects disorganization of functional activity of cortex of large hemispheres of the human brain at geomagnetically disturbed days, which is likely connected with dysfunction of integrative subcortical systems, with disbalance of its ascending synchronizing and desynchronizing influences. Imbalance of activating and deactivating mechanisms including dysfunctions of ergo- and tropho-tropic over-segmentary centers was registered. Strengthening cortical connections in the right cortical hemisphere and their short circuit on temporal sections during geomagnetically disturbed days were observed, while, in geomagnetically quiet days, a profile of correlation interrelations reflected weak internal- and inter-hemispheric connections. The threshold of convulsive (spasmodic readiness of the human brain is reduced, which is especially dangerous for risk group persons. It is established that, in general, weak and moderate geomagnetic storms exert stimulating influence while strong disturbances of geomagnetic conditions activate braking (inhibiting processes.

  9. Geomagnetic Storms and Acute Myocardial Infarctions Morbidity in Middle Latitudes

    Science.gov (United States)

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

    2009-12-01

    Results of collaborative studies on revealing a possible relationship between solar activity (SA) and geomagnetic activity (GMA) and pre-hospital acute myocardial infarction (AMI) morbidity are presented. Studies were based on medical data from Bulgaria and Azerbaijan. Bulgarian data, covering the period from 01.12.1995 to 31.12.2004, concerned daily distribution of number of patients with AMI diagnose (in total 1192 cases) from Sofia Region on the day of admission at the hospital. Azerbaijani data contained 4479 pre-hospital AMI incidence cases for the period 01.01.2003-31.12.2005 and were collected from 21 emergency and first medical aid stations in Grand Baku Area (including Absheron Economical Region with several millions of inhabitants). Data were "cleaned" as much as possible from social and other factors and were subjected to medical and mathematical/statistical analysis. Medical analysis showed reliability of the used data. Method of ANalysis Of VAriance (ANOVA) was applied to check the significance of GMA intensity effect and the type of geomagnetic storms - those caused by magnetic clouds (MC) and by high speed solar wind streams (HSSWS) - on AMI incidences. Relevant correlation coefficients were calculated. Results were outlined for both considered data. Results obtained for the Sofia data showed statistically significant positive correlation between considered GMA indices and AMI occurrence. ANOVA revealed that AMI incidence number was significantly increased from the day before till the day after geomagnetic storms with different intensities. Geomagnetic storms caused by MC were related to significant increase of AMI number in comparison with the storms caused by HSSWS. There was a trend for such different effects even on -1st and +1st day for the period 1995-2004. Results obtained for the Baku data revealed trends similar to those obtained for Sofia data. AMI morbidity increment was observed on the days with higher GMA intensity and after these days

  10. Gulmarg, Kashmir, India: Potential Site for Optical Astronomical Observations

    Indian Academy of Sciences (India)

    Ajaz Ahmad Dar; Manzoor A. Malik

    2017-06-01

    The site characteristics of Gulmarg, Kashmir at an altitude of about 2743.2 m above sea level is based on analysis of meteorological conditions, cloud cover, temperature, wind speed, wind direction, relative humidity and atmospheric pressure, etc. Analysis and characterization of meteorological conditions suggest that Gulmarg, Kashmir is a potential site for carrying out photometric as well as spectroscopic observations of celestial objects.

  11. L-shell bifurcation of electron outer belt at the recovery phase of geomagnetic storm as observed by STEP-F and SphinX instruments onboard the CORONAS-Photon satellite

    Science.gov (United States)

    Dudnik, Oleksiy; Sylwester, Janusz; Kowalinski, Miroslaw; Podgorski, Piotr

    2016-07-01

    Radiation belts and sporadically arising volumes comprising enhanced charged particle fluxes in the Earth's magnetosphere are typically studied by space-borne telescopes, semiconductor, scintillation, gaseous and other types of detectors. Ambient and internal electron bremsstrahlung in hard X-ray arises as a result of interaction of precipitating particles with the atmosphere (balloon experiments) and with the satellite's housings and instrument boxes (orbital experiments). Theses emissions provide a number of new information on the physics of radiation belts. The energies of primary electrons and their spectra responsible for measured X-ray emissions remain usually unknown. Combined measurements of particle fluxes, and their bremsstrahlung by individual satellite instruments placed next to each other provide insight to respective processes. The satellite telescope of electrons and protons STEP-F and the solar X-ray spectrophotometer SphinX were placed in close proximity to each other aboard CORONAS-Photon, the low, circular and highly inclined orbit satellite. Based on joint analysis of the data we detected new features in the high energy particle distributions of the Earth's magnetosphere during deep minimum of solar activity [1-3]. In this research the bifurcation of Van Allen outer electron radiation belt during the weak geomagnetic storm and during passage of interplanetary shock are discussed. Outer belt bifurcation and growth of electron fluxes in a wide energy range were recorded by both instruments during the recovery phase of May 8, 2009 substorm. STEP-F recorded also barely perceptible outer belt splitting on August 5, 2009, after arrival of interplanetary shock to the Earth's magnetosphere bowshock. The STEP-F and SphinX data are compared with the space weather indexes, and with relativistic electron fluxes observed at geostationary orbit. We discuss possible mechanism of the phenomena consisting in the splitting of drift shells because of Earth

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

    Science.gov (United States)

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

    2017-02-01

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

  13. Electric Utility Industry Experience with Geomagnetic Disturbances

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Electric utility industry experience with geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-09-01

    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.

  15. Electric utility industry experience with geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-09-01

    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.

  16. Electric utility industry experience with geomagnetic disturbances

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-09-01

    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

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-09-01

    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. Observation of cooperatively enhanced atomic dipole forces from NV centers in optically trapped nanodiamonds

    CERN Document Server

    Juan, M L; Besga, B; Brennen, G; Molina-Terriza, G; Volz, T

    2015-01-01

    Since the early work by Ashkin in 1970, optical trapping has become one of the most powerful tools for manipulating small particles, such as micron sized beads or single atoms. The optical trapping mechanism is based on the interaction energy of a dipole and the electric field of the laser light. In atom trapping, the dominant contribution typically comes from the allowed optical transition closest to the laser wavelength, whereas for mesoscopic particles it is given by the bulk polarizability of the material. These two different regimes of optical trapping have coexisted for decades without any direct link, resulting in two very different contexts of applications: one being the trapping of small objects mainly in biological settings, the other one being dipole traps for individual neutral atoms in the field of quantum optics. Here we show that for nanoscale diamond crystals containing artificial atoms, so-called nitrogen vacancy (NV) color centers, both regimes of optical trapping can be observed at the same...

  19. Optical polarization observations in Hogg 22 and NGC 6204

    Science.gov (United States)

    Martínez, R.; Vergne, M. M.; Feinstein, C.

    2004-06-01

    We present new (UBVRI) multicolor linear polarimetric data for 22 of the brightest stars in the area of the open clusters Hogg 22 and NGC 6204 to study the properties of the ISM (interstellar medium) toward these clusters and between them. The new data were incorporated in our data set of previous observations (Waldhausen et al. \\cite{waldhausen}), resulting in 28 observed stars in the region. Our data yield for NGC 6204 a mean polarization percentage of Pλ_max˜1.8%, close to the polarization value produced by the ISM with normal efficiency (Pλ_max ˜ 5 EB-V) with a color excess of EB-V =0.51. Meanwhile for Hogg 22, located behind NGC 6204, the mean polarization is Pλ_max˜ 2.15%, lower than the expected value for the observed color excess of EB-V =0.68 (Forbes et al. 1996) and the average efficiency of polarization for the interstellar dust. The mean angle of the polarization vectors of Hogg 22 is θ=44.9 °, which agrees with the expected angle produce by dust particles aligned in the direction of the Galactic Plane (θ=48°), while for NGC 6204 a lower value, θ=33.7 °, was found. Therefore, we believe that Hogg 22 is depolarized by the same dust that is polarizing NGC 6204, due to different orientations of the dust particles (and magnetic fields) that polarize the starlight. Based on observations obtanined at Complejo Astronómico El Leoncito (CASLEO), operated under agreement between the CONICET and the National Universities of La Plata, Córdoba, and San Juan, Argentina.

  20. Optical observations of XTE J1709-267

    Science.gov (United States)

    Wiersema, K.; Higgins, A. B.

    2016-06-01

    The X-ray binary XTE J1709-267 was recently found to be in outburst again by MAXI (Atel #9108). We observed this source using EFOSC2 on the ESO NTT. At 02:33 UT on 23 June 2016, the source was detected at V=17.9 mag. This is several magnitudes brighter than the brightness in quiescence (Jonker et al. 2004, MNRAS 354, 666).

  1. Progress cargo spacecraft observed with the AZT-33IK optical telescope

    Science.gov (United States)

    Klunko, Evgeniy; Eselevich, Maksim; Tergoev, Vladimir

    2016-09-01

    In this paper, we describe a telescope and measuring equipment used for optical observations of Progress cargo spacecraft (PCS), which were made during Radar-Progress space experiment sessions. We also describe object tracking and measurement techniques. The observations were made with the optical telescope AZT-33IK at Sayan Solar Observatory of ISTP SB RAS. During many of the sessions, we registered optical phenomena that occurred in regions of space surrounding PCS and appeared due to the work of PCS onboard engines. The data we obtained can be used to independently control the geometry of the experiment and to analyze physical conditions in outer space.

  2. History of the geomagnetic field

    Science.gov (United States)

    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.

  3. Multiband Optical Observation of P/2010 A2 Dust Tail

    CERN Document Server

    Kim, Junhan; Hanayama, Hidekazu; Hasegawa, Sunao; Usui, Fumihiko; Yanagisawa, Kenshi; Sarugaku, Yuki; Watanabe, Jun-ichi; Yoshida, Michitoshi

    2012-01-01

    An inner main-belt asteroid, P/2010 A2, was discovered on January 6th, 2010. Based on its orbital elements, it is considered that the asteroid belongs to the Flora collisional family, where S-type asteroids are common, whilst showing a comet-like dust tail. Although analysis of images taken by the Hubble Space Telescope and Rosetta spacecraft suggested that the dust tail resulted from a recent head-on collision between asteroids (Jewitt et al. 2010; Snodgrass et al. 2010), an alternative idea of ice sublimation was suggested based on the morphological fitting of ground-based images (Moreno et al. 2010). Here, we report a multiband observation of P/2010 A2 made on January 2010 with a 105 cm telescope at the Ishigakijima Astronomical Observatory. Three broadband filters, $g'$, $R_c$, and $I_c$, were employed for the observation. The unique multiband data reveals that the reflectance spectrum of the P/2010 A2 dust tail resembles that of an Sq-type asteroid or that of ordinary chondrites rather than that of an S-...

  4. The quasi-biennial variation in the geomagnetic field: a global characteristics analysis

    Science.gov (United States)

    Ou, Jiaming; Du, Aimin

    2016-04-01

    The periodicity of 1.5-3 years, namely the quasi-biennial oscillation (QBO), has been identified in the solar, geophysical, and atmospheric variability. Sugiura (1976) investigated the observatory annual means over 1900-1970 and confirmed the QBO in the geomagnetic field. At present, studying the quasi-biennial oscillation becomes substantial for separating the internal/external parts in the geomagnetic observations. For the internal field, two typical periodicities, namely the 6-year oscillation in the geomagnetic secular acceleration (SA) and the geomagnetic jerk (occurs in 1-2 years), have close period to the QBO. Recently, a global quasi-biennial fluctuation was identified in the geomagnetic core field model (Silva et al., 2012). Silva et al. speculated this 2.5 years signal to either external source remaining in the core field model or consequence of the methods used to construct the model. As more high-quality data from global observatories are available, it is a good opportunity to characterize the geomagnetic QBO in the global range. In this paper, we investigate the QBO in the observatory monthly geomagnetic field X, Y, and Z components spanning 1985-2010. We employ the observatory hourly means database from the World Data Center for Geomagnetism (WDC) for the investigation. Wavelet analysis is used to detect and identify the QBO, while Fast Fourier Transform (FFT) analysis to obtain the statistics of the QBO. We apply the spherical harmonic analysis on QBO's amplitude, in order to quantify and separate internal and external sources. Three salient periods respectively at 2.9, 2.2, and 1.7 years, are identified in the amplitude spectrum over 1988-2008. The oscillation with the period of ~2.2 years is most prominent in all field components and further studied. In the X component the QBO is attenuated towards the polar regions, while in the Z component the amplitude of QBO increases with increasing of the geomagnetic latitude. At the high latitudes, the QBO

  5. Effect of Cross-Correlation on Geomagnetic Forecast Accuracies

    Science.gov (United States)

    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.

  6. SOAR Adaptive Optics Observations of the Globular Cluster NGC6496

    CERN Document Server

    Fraga, Luciano; Tokovinin, Andrei

    2013-01-01

    We present high-quality BVRI photometric data in the field of globular cluster NGC 6496 obtained with the SOAR Telescope Adaptive Module (SAM). Our observations were collected as part of the ongoing SAM commissioning. The distance modulus and cluster color excess as found from the red clump is $\\mMv = 15.71 \\pm 0.02$\\,mag and $\\EVI = 0.28 \\pm 0.02$\\,mag. An age of $10.5 \\pm 0.5$\\,Gyr is determined from the difference in magnitude between the red clump and the subgiant branch. These parameters are in excellent agreement with the values derived from isochrone fitting. From the color-magnitude diagram we find a metallicity of $\\feh = -0.65$\\,dex and hence support a disk classification for NGC 6496. The complete $BVRI$ data set for NGC 6469 is made available in the electronic edition of the Journal.

  7. Soar adaptive optics observations of the globular cluster NGC 6496

    Energy Technology Data Exchange (ETDEWEB)

    Fraga, Luciano [Southern Observatory for Astrophysical Research, Casilla 603, La Serena (Chile); Kunder, Andrea; Tokovinin, Andrei, E-mail: lfraga@ctio.noao.edu, E-mail: lfraga@lna.br [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)

    2013-06-01

    We present high-quality BVRI photometric data in the field of globular cluster NGC 6496 obtained with the SOAR Telescope Adaptive Module (SAM). Our observations were collected as part of the ongoing SAM commissioning. The distance modulus and cluster color excess as found from the red clump are (m – M) {sub V} = 15.71 ± 0.02 mag and E(V – I) = 0.28 ± 0.02 mag. An age of 10.5 ± 0.5 Gyr is determined from the difference in magnitude between the red clump and the subgiant branch. These parameters are in excellent agreement with the values derived from isochrone fitting. From the color-magnitude diagram we find a metallicity of [Fe/H] = –0.65 dex and hence support a disk classification for NGC 6496. The complete BVRI data set for NGC 6469 is made available in the electronic edition of the Journal.

  8. Optical observation of discharge in resistive plate chamber

    CERN Document Server

    Kitayama, I; Teramoto, Y; Chinomi, S; Inoue, Y; Nakano, E; Takahashi, T

    1999-01-01

    Pictures of the discharge in a resistive plate chamber (RPC) were taken using a glass RPC, an image intensifier and a CCD camera. Measurements were separately made for cosmic rays (trigger mode) and self-discharge (non-tigger mode), in vertical and horizontal views, operated in the streamer mode with various gas mixtures. Streamers are observed as narrow strings with diameters <500 mu m, extending between the anode and the cathode surfaces. Each streamer accompanies disk-shaped discharges of 2-4 mm diameter, on both the cathode and the anode surfaces. With a gas mixture that gives a high detection efficiency, discharge patterns are similar for both the cosmic rays and self-discharges.

  9. Observing Nanometre Scale Particles with Light Scattering for Manipulation Using Optical Tweezers

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jin-Hua; Qu Lian-Jie; Yao Kun; ZHONG Min-Cheng; LI Yin-Mei

    2008-01-01

    Nanometre-scale particles can be manipulated using optical tweezers,but cannot be directly observed.We Drasent a simple method that nanoparticles can be directly observed using optical tweezers combined with dark field microscopy.A laser beam perpendicular to a tightly focused laser beam for trap illuminates specimen and does not enter objective,nanoparticles in focal plane all can be directly observed in dark field because of light scattering.It is implemented that the polystyrene beads of diameter 100nm can be directly observed and trapped.

  10. Simultaneous optical and radar observations of meteor head-echoes utilizing SAAMER

    Science.gov (United States)

    Michell, R. G.; Janches, D.; Samara, M.; Hormaechea, J. L.; Brunini, C.; Bibbo, I.

    2015-12-01

    We present simultaneous optical and radar observations of meteors observed with the Southern Argentine Agile MEteor Radar (SAAMER). Although such observations were performed in the past using High Power and Large Aperture radars, the focus here is on meteors that produced head echoes that can be detected by a significantly less sensitive but more accessible radar system. An observational campaign was conducted in August of 2011, where an optical imager was operated near the radar site in Rio Grande, Tierra del Fuego, Argentina. Six head echo events out of 150 total detections were identified where simultaneous optical meteors could also be clearly seen within the main radar beam. The location of the meteors derived from the radar interferometry agreed very well with the optical location, verifying the accuracy of the radar interferometry technique. The meteor speeds and origin directions calculated from the radar data were accurate-compared with the optics-for the 2 meteors that had radar signal-to-noise ratios above 2.5. The optical meteors that produced the head echoes had horizontal velocities in the range of 29-91 km/s. These comparisons with optical observations improve the accuracy of the radar detection and analysis techniques, such that, when applied over longer periods of time, will improve the statistics of southern hemisphere meteor observations. Mass estimates were derived using both the optical and radar data and the resulting masses agreed well with each other. All were within an order of magnitude and in most cases, the agreement was within a factor of two.

  11. PAMELA's measurements of geomagnetic cutoff variations during the 14 December 2006 storm

    CERN Document Server

    Adriani, O; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mikhailov, M Mergé V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N

    2016-01-01

    Data from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) satellite experiment were used to measure the geomagnetic cutoff for high-energy (>80 MeV) protons during the 14 December 2006 geomagnetic storm. The variations of the cutoff latitude as a function of rigidity were studied on relatively short timescales, corresponding to spacecraft orbital periods (94 min). Estimated cutoff values were compared with those obtained by means of a trajectory tracing approach based on a dynamical empirical modeling of the Earth's magnetosphere. We found significant variations in the cutoff latitude, with a maximum suppression of about 7 deg at lowest rigidities during the main phase of the storm. The observed reduction in the geomagnetic shielding and its temporal evolution were related to the changes in the magnetospheric configuration, investigating the role of interplanetary magnetic field, solar wind and geomagnetic parameters. PAMELA's results represent the first direct measurement...

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

    Science.gov (United States)

    Mikulecky, M; Moravcikova, C; Czanner, S

    1996-08-01

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

  13. Early optical observations of GRBs by the TAROT telescopes: period 2001-2008

    CERN Document Server

    Klotz, A; Atteia, J L; Gendre, B

    2009-01-01

    The TAROT telescopes (Telescopes a Action Rapide pour les Objets Transitoires) are two robotic observatories designed to observe the prompt optical emission counterpart and the early afterglow of gamma ray bursts (GRBs). We present data acquired between 2001 and 2008 and discuss the properties of the optical emission of GRBs, noting various interesting results. The optical emission observed during the prompt GRB phase is rarely very bright: we estimate that 5% to 20% of GRBs exhibit a bright optical flash (R<14) during the prompt gamma-ray emission, and that more than 50% of the GRBs have an optical emission fainter than R=15.5 when the gamma-ray emission is active. We study the apparent optical brightness distribution of GRBs at 1000 s showing that our observations confirm the distribution derived by other groups. The combination of these results with those obtained by other rapid slewing telescopes allows us to better characterize the early optical emission of GRBs and to emphasize the importance of very...

  14. Manufacturing of advanced bent crystals for Laue Optics for Gamma ObservationS (LOGOS)

    Energy Technology Data Exchange (ETDEWEB)

    Mazzolari, Andrea, E-mail: mazzolari@fe.infn.it [Department of Physics and Earth Sciences, University of Ferrara, Via Saragat 1/c, 44122 Ferrara (Italy); INFN, Section of Ferrara (Italy); Camattari, Riccardo; Bellucci, Valerio; Paternò, Gianfranco [Department of Physics and Earth Sciences, University of Ferrara, Via Saragat 1/c, 44122 Ferrara (Italy); INFN, Section of Ferrara (Italy); Scian, Carlo; Mattei, Giovanni [University of Padova, Department of Physics and Astronomy Galileo Galilei (Italy); Guidi, Vincenzo [Department of Physics and Earth Sciences, University of Ferrara, Via Saragat 1/c, 44122 Ferrara (Italy); INFN, Section of Ferrara (Italy)

    2015-07-15

    X- and γ-ray detection is currently a hot topic for a wide scientific community, spanning from astrophysics to nuclear medicine. However, lack of optics capable of focusing photons of energies in the energy range 0.1–1 MeV leaves the photon detection to a direct-view approach, resulting in a limited efficiency and resolution. The main scope of the INFN-LOGOS project is the development of technologies that enable manufacturing highly performing optical elements to be employed in the realization of hard X-ray lenses. Such lenses, typically named Laue lenses, consist of an ensemble of crystals disposed in concentric rings in order to diffract the incident radiation towards the focus of the lens, where a detector is placed. In particular, the INFN-LOGOS project aims at the realization of intrinsically bent silicon and germanium crystals exploiting the quasi-mosaic effect for focusing hard X-rays. Crystal manufacturing relies on a proper revisitation of techniques typically employed in silicon micromachining, such as thin film deposition and patterning or ion implantation.

  15. Optical spectroscopic observations of $\\gamma$-ray blazar candidates VI. Further observations from TNG, WHT, OAN, SOAR and Magellan telescopes

    CERN Document Server

    Crespo, N Álvarez; Milisavljevic, D; Landoni, M; Chavushyan, V; Patiño-Álvarez, V; Masetti, N; Jiménez-Bailón, E; Strader, J; Chomiuk, L; Katagiri, H; Kagaya, M; Cheung, C C; Paggi, A; D'Abrusco, R; Ricci, F; La Franca, F; Smith, Howard A; Tosti, G

    2016-01-01

    Blazars, one of the most extreme class of active galaxies, constitute so far the largest known population of $\\gamma$-ray sources and their number is continuously growing in the Fermi catalogs. However in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidate of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition about 1/3 of the $\\gamma$-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower energy counterpart. Since 2012 we have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 $\\gamma$-ray blazar candidates from different observing programs we carried out with the TNG, WHT, OAN, SOAR and Magellan telescopes. We found that 21 out of 30 sour...

  16. Centennial to millennial geomagnetic field variations

    Directory of Open Access Journals (Sweden)

    Muscheler Raimund

    2012-06-01

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

  17. Improved geomagnetic referencing in the Arctic environment

    Science.gov (United States)

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

    2016-01-01

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

  18. Optically selected fossil groups; X-ray observations and galaxy properties

    CERN Document Server

    Khosroshahi, Habib G; Rasmussen, Jesper; Molaeinezhad, Alireza; Ponman, Trevor; Dariush, Ali A; Sanderson, Alastair J R

    2014-01-01

    We report on the X-ray and optical observations of galaxy groups selected from the 2dfGRS group catalog, to explore the possibility that galaxy groups hosting a giant elliptical galaxy and a large optical luminosity gap present between the two brightest group galaxies, can be associated with an extended X-ray emission, similar to that observed in fossil galaxy groups. The X-ray observations of 4 galaxy groups were carried out with Chandra telescope with 10-20 ksec exposure time. Combining the X-ray and the optical observations we find evidences for the presence of a diffuse extended X-ray emission beyond the optical size of the brightest group galaxy. Taking both the X-ray and the optical criteria, one of the groups is identified as a fossil group and one is ruled out because of the contamination in the earlier optical selection. For the two remaining systems, the X-ay luminosity threshold is close to the convention know for fossil groups. In all cases the X-ray luminosity is below the expected value from the...

  19. Observation of Fundamental Thermal Noise in Optical Fibers down to Infrasonic Frequencies

    CERN Document Server

    Dong, Jing; Li, Tang; Liu, Liang

    2015-01-01

    The intrinsic thermal noise in optical fibers is the ultimate limit of fiber-based systems. However, at infrasonic frequencies, the spectral behavior of the intrinsic thermal noise remains unclear so far. We present the measurements of the fundamental thermal noise in optical fibers obtained using a balanced fiber Michelson interferometer. When an ultra-stable laser is used as the laser source and other noise sources are carefully controlled, the 1/f spectral density of thermal noise is observed down to infrasonic frequencies and the measured magnitude is consistent with the theoretical predictions at the frequencies from 0.2 Hz to 20 kHz. Moreover, as observed in the experiment, the level of 1/f thermal noise is reduced by changing the coating of optical fibers. Therefore, a possible way to reduce the thermal noise in optical fibers at low Fourier frequencies is indicated. Finally, the inconsistency between the experimental data on thermomechanical noise and existing theory is discussed.

  20. Joint radio and optical observations of the most radio-powerful intracloud lightning discharges

    Directory of Open Access Journals (Sweden)

    A. R. Jacobson

    2013-03-01

    Full Text Available The most radio-powerful intracloud lightning emissions are associated with a phenomenon variously called "narrow bipolar events" or "compact intracloud discharges". This article examines in detail the coincidence and timing relationship between, on the one hand, the most radio-powerful intracloud lightning events and, on the other hand, optical outputs (or lack thereof of the same discharge process. This is done, first, using coordinated very high frequency (VHF and optical observations from the FORTE satellite and, second, using coordinated sferic and all-sky optical observations from the Los Alamos Sferic Array. In both cases, it is found that the sought coincidences are exceedingly rare. Moreover, in the handful of coincidences between optical and intense radio emissions that have been identified, the radio emissions differ from their usual behavior, by being accompanied by approximately simultaneous "conventional" lightning radio emissions. It is implied that the most radio-powerful intracloud emission process essentially differs from ordinary incandescent lightning.

  1. Direct observation of Rogue Waves in optical turbulence using Time Microscopy

    CERN Document Server

    Suret, Pierre; Tikan, Alexey; Evain, Clement; Randoux, Stephane; Szwaj, Christophe; Bielawski, Serge

    2016-01-01

    The formation of coherent structures in noise driven phenomena and in Turbulence is a complex and fundamental question. A particulary important structure is the so-called Rogue Wave (RW) that arises as the sudden appearance of a localized and giant peak. First studied in Oceanography, RWs have been extensively investigated in Optics since 2007, in particular in optical fibers experiments on supercontinua and optical turbulence. However the typical time scales underlying the random dynamics in those experiments prevented --up to now-- the direct observation of isolated RWs. Here we report on the direct observation of RWs, using an ultrafast acquisition system equivalent to microscope in the time domain. The RWs are generated by nonlinear propagation of random waves inside an optical fiber, and recorded with $\\sim 250$~fs resolution. Our experiments demonstrate the central role played by "breathers-like" solutions of the one-dimensional nonlinear Schr\\"odinger equation (1D-NLSE) in the formation of RWs

  2. Optical outburst of 4C 38.41 (1633+382) observed by the GASP

    Science.gov (United States)

    Raiteri, C. M.; Villata, M.; Ehgamberdiev, Sh. A.; Mirzaqulov, D. O.; Holikov, Sh.

    2011-07-01

    The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reports on the recent observation of a strong optical brightening of the gamma-loud quasar 4C 38.41. This is one of the 28 blazars for which the GASP performs a long-term, multiwavelength monitoring. In the current optical observing season, the source has shown multiwavelength activity (see also ATels #3238, #3333, #3335, #3360), so that the GASP has intensified the observations with a dedicated campaign (contact person: C.

  3. Experimental observation of disorder induced self-focusing in optical fibers

    Energy Technology Data Exchange (ETDEWEB)

    Leonetti, Marco, E-mail: marco.leonetti@roma1.infn.it [Center for Life Nano Science@Sapienza, Istituto Italiano di Tecnologia, Viale Regina Elena, 291 00161 Roma (Italy); Karbasi, Salman [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States); Mafi, Arash [Department of Physics and Astronomy and Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Conti, Claudio [ISC-CNR and Department of Physics, University Sapienza, P.le Aldo Moro 5, I-00185, Roma (Italy)

    2014-10-27

    We observed disorder induced focusing nonlinearity activated by a monochromatic light beam in optical fibers composed by two kinds of plastics. The two materials, arranged in disordered fashion, support modes with a degree of localization which increases with the intensity of the optical beam. The temporal response of the optical fiber demonstrates the thermal origin of this nonlinearity. Measurements of the localization length as a function of the input power with broadband and monochromatic inputs show the effectiveness of focusing action with respect to the case of homogeneous fibers.

  4. Observation of SERS effect in Raman optical activity, a new tool for chiral vibrational spectroscopy

    DEFF Research Database (Denmark)

    Abdali, Salim

    2006-01-01

    A new tool for chiral vibrational spectroscopy is here reported. A Surface Enhanced effect was observed using Raman Optical Activity (ROA). This observation opens new possibilities for ROA as a tool for vibrational spectroscopy. The combination of surface enhanced effect SE and ROA into SEROA...

  5. Minimax confidence intervals in geomagnetism

    Science.gov (United States)

    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.

  6. Optical historical maximum of the blazar PKS 1510-08 observed by the GASP

    Science.gov (United States)

    Larionov, V. M.; Villata, M.; Raiteri, C. M.; Arkharov, A. A.; Konstantinova, T. S.; Kopatskaya, E. N.; Larionova, E. G.; Blinov, D.; Melnichuk, D.; Troitsky, I.

    2009-03-01

    With reference to ATel #1988 (and references therein) on the optical and near-IR brightening of the blazar PKS 1510-08, the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reports that the source has further brightened by almost 1 mag in the last 3 days, reaching R = 14.35 ± 0.03 on March 27.1. As far as we know, this is the brightest optical state ever observed for this object.

  7. Instrumentation set-up for the observation of astrophysical optical transients at solar furnace of Almeria

    Energy Technology Data Exchange (ETDEWEB)

    Piccioni, A.; Bartolini, C.; Cosentino, G.; Guarnieri, A.; Beskin, G.; La Panda, C.; Nanni, D.

    2002-07-01

    The choice of the solar Furnace of Almeria (SFA) as light collector for astronomical observations of Optical transients (OTs) sets firm instrumental constraints. The structure of special instrumentation based on wide field panoramic detectors is analyzed in correspondence with present optical resolution. In view of future developments at the facilities of Plataforma Solar de Almeria (PSA) two high speed photometer configurations are discussed with reference to reduction of costs and complexity. (Author) 13 refs.

  8. Solar wind and geomagnetism. Toward a standard classification of geomagnetic activity from 1868 to 2009

    Energy Technology Data Exchange (ETDEWEB)

    Zerbo, J.L. [Univ. Polytechnique de Bobo Dioulasso (Burkina Faso); UPMC/Polytechique/CNRS, UMR 7648, Saint-Maur-des-Fosses (France). LPP-Lab. de Physique des Plasmas; Mazaudier, C. Amory [UPMC/Polytechique/CNRS, UMR 7648, Saint-Maur-des-Fosses (France). LPP-Lab. de Physique des Plasmas; Ouattara, F. [Koudougou Univ. (Burkina Faso). Ecole Normale Superieure; Richardson, J.D. [M.I.T., Cambridge, MA (United States). Center for Space Research

    2012-07-01

    We examined solar activity with a large series of geomagnetic data from 1868 to 2009. We have revisited the geomagnetic activity classification scheme of Legrand and Simon (1989) and improve their scheme by lowering the minimum Aa index value for shock and recurrent activity from 40 to 20 nT. This improved scheme allows us to clearly classify about 80% of the geomagnetic activity in this time period instead of only 60% for the previous Legrand and Simon classification. (orig.)

  9. Differential rotation of geomagnetic field

    Institute of Scientific and Technical Information of China (English)

    WEI Zigang; XU Wenyao

    2003-01-01

    The latitudinal dependence of the westward drift in the main geomagnetic field is examined by using the correlation analysis of moving random pattern. The study reveals the characteristics in the differential rotation of the main field. The results show that the global geomagnetic field drifts westward with an average speed of 0.18°/a during 1900-2000. The westward drift rate is not symmetrical with respect to the equator. The maximum westward drift rate, 0.31°/a, occurs at the latitude --= -15°, forming a Rapid Westward Drift Belt (RDB) around this latitude. Going northward and southward from this belt, the drift rate decreases and reaches the minimum (0.12°/a) at --= 50° and the minimum (0.14°/a) at --= -56°, forming a Northern Hemisphere Slow Westward Drift Belt (N-SDB) and a Southern Hemisphere Slow Westward Drift Belt (S-SDB). Three phases can be detected in the evolution of the westward drift. In the first phase (1900-1940), the RDB dominates the global drift pattern. The westward drifts in this belt are much faster than those in other areas. In the second phase (1940-1960), the drift rates in the RDB are less than those in the first phase, while the drifts in the N-SDB and S-SDB are relatively large. In this phase, the differential rotation becomes less obvious. In the third phase (1960-2000), the westward drift in the RDB increases again and the differential rotation gradually becomes apparent.

  10. High-latitude geomagnetic studies (22-23 millihertz)

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, A. (AT T Bell Laboratories, Murray Hill, NJ (USA) City Univ. of New York, Brooklyn (USA)); Lanzerotti, L.J.; Maclennan, C.C.; Medford, L.V. (AT T Bell Laboratories, Murray Hill, NJ (USA))

    1988-01-01

    Geomagnetic field measurements were initiated at Iqaluit (formerly Frobisher Bay) in the Northwest Territories of Canada during July 1985 (Wolfe et al. 1986). This site was selected because it was calculated to be in the conjugate area to the Amundsen-Scott South Pole Station where extensive geomagnetic research has been conducted. The principal scientific objectives are to study the conjugacy of high-latitude magnetic fluctuations observed at Iqaluit and South Pole (L{approximately}13). In this report, the authors extend the previous report of Wolfe et al. (1987) and comment upon the conjugacy of the stations for magnetic field fluctuations in the Pc3 (22-33 millihertz) hydromagnetic regime and upon the penetration of hydromagnetic energy deeper into the magnetosphere on the local dayside.

  11. De-noising Diurnal Variation Data in Geomagnetic Field Modelling

    Science.gov (United States)

    Onovughe, E.

    2017-01-01

    Ground based geomagnetic observatory series have been used to investigate and describe the residuals between a continuous geomagnetic field model and observed diurnal variation for noise-removal of signal due to external field of magnetospheric ring current sources. In all the observatories studied, the residuals in the X-direction consistently show the noisiest signal. Results show that the residuals in the X-direction correlates closely with the RC-index, suggesting an origin from unmodelled external field variation. Notable cross-correlation is also seen between the residuals and the RC-index at zero-lag. Removal/reduction of this unmodelled signal enhances resolution of fine-scale detail in diurnal variation studies.

  12. PAMELA's measurements of geomagnetically trapped and albedo protons

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bravar, U; Cafagna, F; Campana, D; Carbone, R; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Formato, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Lee, M; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergè, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Zverev, V G

    2015-01-01

    Data from the PAMELA satellite experiment were used to perform a detailed measurement of under-cutoff protons at low Earth orbits. On the basis of a trajectory tracing approach using a realistic description of the magnetosphere, protons were classified into geomagnetically trapped and re-entrant albedo. The former include stably-trapped protons in the South Atlantic Anomaly, which were analyzed in the framework of the adiabatic theory, investigating energy spectra, spatial and angular distributions; results were compared with the predictions of the AP8 and the PSB97 empirical trapped models. The albedo protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and un-trapped, spreading over all latitudes and including both short-lived (precipitating) and long-lived (pseudo-trapped) components. Features of the penumbra region around the geomagnetic cutoff were investigated as well. PAMELA observations significantly improve the characterization of the high energy proton populat...

  13. Geomagnetic Secular Variation Prediction with Thermal Heterogeneous Boundary Conditions

    Science.gov (United States)

    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.

  14. Remagnetization of lava flows spanning the last geomagnetic reversal

    Science.gov (United States)

    Vella, Jérôme; Carlut, Julie; Valet, Jean-Pierre; Goff, Maxime Le; Soler, Vicente; Lopes, Fernando

    2017-08-01

    Large directional changes of remanent magnetization within lava flows that cooled during geomagnetic reversals have been reported in several studies. A geomagnetic scenario implies extremely rapid geomagnetic changes of several degrees per day, thus difficult to reconcile with the rate of the earth's core liquid motions. So far, no complete rock magnetic model provides a clear explanation. We revisited lava flows sandwiched between an underlying reverse and an overlying normal polarity flow marking the last reversal in three distinct volcanic sequences of the La Palma Island (Canary archipelago, Spain) that are characterized by a gradual evolution of the direction of their remanent magnetization from bottom to top. Cleaning efficiency of thermal demagnetization was not improved by very rapid heating and cooling rates as well as by continuous demagnetization using a Triaxe magnetometer. We did not observe partial self-reversals and minor changes in magnetic grain sizes are not related to the within-flow directional changes. Microscopic observations indicate poor exsolution, which suggests post-cooling thermochemical remagnetization processes. This scenario is strongly reinforced by laboratory experiments that show large resistance to thermal demagnetization when thermoremanence was acquired over a long time period. We speculate that in the present situation exsolution was reactivated during in field reheating and yielded formation of new magnetite, yet magnetic domain state rearrangements could also play a role. Initial reheating when the overlying flow took place, albeit moderate (less than 200-300 °C), was enough to produce overlying components with significantly higher unblocking temperatures.

  15. A new regard about Surlari National Geomagnetic Observatory

    Science.gov (United States)

    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

  16. Ukrainian network of Optical Stations for man-made space objects observation

    Science.gov (United States)

    Sybiryakova, Yevgeniya

    2016-07-01

    The Ukrainian Network of Optical Stations (UNOS) for man-made objects research was founded in 2012 as an association of professional astronomers. The main goals of network are: positional and photometric observations of man-made space objects, calculation of orbital elements, research of shape and period of rotation. The network consists of 8 stations: Kiev, Nikolaev, Odesa, Uzhgorod, Lviv, Yevpatoriya, Alchevsk. UNOS has 12 telescopes for observation of man-made space objects. The new original methods of positional observation were developed for optical observation of geosynchronous and low earth orbit satellites. The observational campaigns of LEO satellites held in the network every year. The numerical model of space object motion, developed in UNOS, is using for orbit calculation. The results of orbital elements calculation are represented on the UNOS web-site http://umos.mao.kiev.ua/eng/. The photometric observation of selected objects is also carried out in network.

  17. The Platform Design of Space-based Optical Observations of Space Debris

    Science.gov (United States)

    Bing-er, Chen; Jian-ning, Xiong

    2017-01-01

    The basic method to design a platform for the space-based optical observations of space debris is introduced. The observation schemes of GEO (geosynchronous equatorial orbit) and LEO (low Earth orbit) debris are given respectively, including the orbital parameters of platforms and the pointing of telescopes, etc. The debris studied here are all taken from the foreign catalog. According to the real orbits of space debris, the observational results of different schemes are simulated. By studying the single platform, the optimal observing altitude for the GEO debris and the optimal telescope's deflection angles at different altitudes for the LEO debris are given. According to these, the multi-platform observation networks are designed. By analyzing the advantages and disadvantages of different schemes, it can provide a reference for the application of space-based optical observations of space debris

  18. Development of emulsion track expansion techniques for optical-microscopy-observation of low-velocity ion tracks with ranges beyond optical resolution limit

    Energy Technology Data Exchange (ETDEWEB)

    Naka, T. [F-lab., Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Natsume, M. [F-lab., Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)], E-mail: natsume@flab.phys.nagoya-u.ac.jp; Niwa, K.; Hoshino, K.; Nakamura, M.; Nakano, T.; Sato, O. [F-lab., Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

    2007-11-01

    We succeeded to observe tracks of low-velocity Kr ions, having originally ranges below optical resolution, in a fine grain nuclear emulsion with an optical microscope after expanding the emulsion along the incident direction. This opens up the possibility of tracking low-velocity nuclear recoils from massive dark matter particles using optical microscope scanning systems.

  19. Seoul National University Bright Quasar Survey in Optical (SNUQSO) I: First Phase Observations and Results

    CERN Document Server

    Lee, Induk; Kim, Minjin; Kang, Eugene; Shim, Hyunjin; Richards, Gordon T; Edge, Alastair C; Lee, Myung Gyoon; Park, Changbom; Park, Myeong-Gu

    2008-01-01

    We present results from the first phase of the Seoul National University Bright Quasar Survey in Optical (SNUQSO) as well as its basic observational setup. Previous and current large-area surveys have been successful in identifying many quasars, but they could have missed bright quasars due to their survey design. In order to help complete the census of bright quasars, we have performed spectroscopic observations of new bright quasar candidates selected from various methods based on optical colors, near-infrared colors, radio, and X-ray data. In 2005/2006, we observed 55 bright quasar candidates using the Bohyunsan Optical Echelle Spectrograph (BOES) on the 1.8 m telescope at the Bohyunsan Optical Astronomy Observatory in Korea. We identify 14 quasars/Seyferts from our observation, including an optically bright quasar with i=14.98 mag at z=0.092 (SDSS J003236.59-091026.2). Non-quasar/Seyfert objects are found to be mostly stars, among which there are five M-type stars and one cataclysmic variable. Our result ...

  20. What happens when the geomagnetic field reverses?

    CERN Document Server

    Lemaire, Joseph F

    2012-01-01

    During geomagnetic field reversals the radiation belt high-energy proton populations become depleted. Their energy spectra become softer, with the trapped particles of highest energies being lost first, and eventually recovering after a field reversal. The radiation belts rebuild in a dynamical way with the energy spectra flattening on the average during the course of many millennia, but without ever reaching complete steady state equilibrium between successive geomagnetic storm events determined by southward turnings of the IMF orientation. Considering that the entry of galactic cosmic rays and the solar energetic particles with energies above a given threshold are strongly controlled by the intensity of the northward component of the interplanetary magnetic field, we speculate that at earlier epochs when the geomagnetic dipole was reversed, the entry of these energetic particles into the geomagnetic field was facilitated when the interplanetary magnetic field was directed northward. Unlike in other compleme...

  1. Digitized Historical Geomagnetic Publications in PDF format

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A catalog of 732 historical geomagnetic publications that were at risk of loss have been digitized and converted in pdf documents.

  2. Geomagnetism solid Earth and upper atmosphere perspectives

    CERN Document Server

    Basavaiah, Nathani

    2011-01-01

    This volume elaborates several important aspects of solid Earth geomagnetism. It covers all the basics of the subject, including biomagnetism and instrumentation, and offers a number of practical applications with carefully selected examples and illustrations.

  3. An Efficient Optical Observation Ground Network is the Fundamental basis for any Space Based Debris Observation Segment

    Science.gov (United States)

    Cibin, L.; Chiarini, M.; Annoni, G.; Milani, A.; Bernardi, F.; Dimare, L.; Valsecchi, G.; Rossi, A.; Ragazzoni, R.; Salinari, P.

    2013-08-01

    A matter which is strongly debated in the SSA Community, concerns the observation of Space Debris from Space [1]. This topic has been preliminary studied by our Team for LEO, MEO and GEO orbital belts, allowing to remark a fundamental concept, residing in the fact that to be suitable to provide a functionality unavailable from ground in a cost to performance perspective, any Space Based System must operate in tight collaboration with an efficient Optical Ground Observation Network. In this work an analysis of the different functionalities which can be implemented with this approach for every orbital belt is illustrated, remarking the different achievable targets in terms of population size as a function of the observed orbits. Further, a preliminary definition of the most interesting missions scenarios, together with considerations and assessments on the observation strategy and P/L characteristics are presented.

  4. Features of Pc5 pulsations in the geomagnetic field, auroral luminosity, and Riometer absorption

    Science.gov (United States)

    Belakhovsky, V. B.; Pilipenko, V. A.; Samsonov, S. N.; Lorentsen, D.

    2016-01-01

    Simultaneous morning Pc5 pulsations ( f ~ 3-5 mHz) in the geomagnetic field, aurora intensities (in the 557.7 and 630.0 nm oxygen emissions and the 471.0 nm nitrogen emission), and riometer absorption, were studied based on the CARISMA, CANMOS, and NORSTAR network data for the event of January 1, 2000. According to the GOES-8 satellite observations, these Pc5 geomagnetic pulsations are observed as incompressible Alfvén waves with toroidal polarization in the magnetosphere. Although the Pc5 pulsation frequencies in auroras, the geomagnetic field, and riometer absorption are close to one another, stable phase relationships are not observed between them. Far from all trains of geomagnetic Pc5 pulsations are accompanied by corresponding auroral pulsations; consequently, geomagnetic pulsations are primary with respect to auroral pulsations. Both geomagnetic and auroral pulsations propagate poleward, and the frequency decreases with increasing geomagnetic latitude. When auroral Pc5 pulsations appear, the ratio of the 557.7/630.0 nm emission intensity sharply increases, which indicates that auroral pulsations result from not simply modulated particle precipitation but also an additional periodic acceleration of auroral electrons by the wave field. A high correlation is not observed between Pc5 pulsations in auroras and the riometer absorption, which indicates that these pulsations have a common source but different generation mechanisms. Auroral luminosity modulation is supposedly related to the interaction between Alfvén waves and the region with the field-aligned potential drop above the auroral ionosphere, and riometer absorption modulation is caused by the scattering of energetic electrons by VLF noise pulsations.

  5. The geomagnetic main field and the geodynamo

    Science.gov (United States)

    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.

  6. The International Geomagnetic Reference Field, 2005

    Science.gov (United States)

    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/

  7. Quality-control gas-detector tube readers: optical versus observer

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, H.B. Jr.

    1976-12-01

    The influence of temperature and humidity upon two length-of-stain gas detector tube systems was studied. Length-of-stain tubes were exposed under carefully controlled laboratory conditions, then read by a panel of observers and a newly developed optical tube reader. Data from the study show, generally, good correlation of results between the observer panel and the optical tube reader. Also, the data indicated that temperature and humidity calibration curves or tables were needed for several of the detector tubes. The two detector tube systems were comparable in reliability; however, for detecting a particular gas, one system may be selected over the other.

  8. A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift

    OpenAIRE

    Wu, Jian; Berk, Daniel Vanden; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P.; Gronwall, Caryl; Wesolowski, Sarah; Porterfield, Blair L.

    2012-01-01

    We have compiled a catalog of optically-selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both UVOT and XRT observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~60% which rises to ~85% ...

  9. Observation of an optical vortex beam from a helical undulator in the XUV region.

    Science.gov (United States)

    Kaneyasu, Tatsuo; Hikosaka, Yasumasa; Fujimoto, Masaki; Iwayama, Hiroshi; Hosaka, Masahito; Shigemasa, Eiji; Katoh, Masahiro

    2017-09-01

    The observation of an optical vortex beam at 60 nm wavelength, produced as the second-harmonic radiation from a helical undulator, is reported. The helical wavefront of the optical vortex beam was verified by measuring the interference pattern between the vortex beam from a helical undulator and a normal beam from another undulator. Although the interference patterns were slightly blurred owing to the relatively large electron beam emittance, it was possible to observe the interference features thanks to the helical wavefront of the vortex beam. The experimental results were well reproduced by simulation.

  10. Optical and X-ray observations of the low-mass X-ray binary EXO 0748-676

    Science.gov (United States)

    Thomas, Brian; Corbet, Robin; Augusteijn, Thomas; Callanan, Paul; Smale, Alan P.

    1993-01-01

    Optical and X-ray observations of EXO-676 in late March 1989 are presented. Our optical observations provide some support for the previously observed correlation between the mean optical brightness and light curve morphology. Unexpectedly, the mean X-ray and optical flux levels during this period do not reflect similar system states. The optical counterpart is found to be in an intermediate to low state, while X-ray data imply a bright (high) state. The changed relationship between optical and X-ray fluxes is evidence showing that EXO 0748-676 has possibly evolved. We fail to find correlated variability in simultaneous X-ray and optical observations. The lack of covariability is attributed to the limited simultaneous coverage of the source and/or significant geometric modulation in the optical light curve.

  11. Geomagnetic disturbance effects on power systems

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. World first complex optical instrumental observations of aurora in the Arctic in 1899−1900

    Directory of Open Access Journals (Sweden)

    L. S. Yevlashin

    2005-07-01

    Full Text Available This report presents data and analysis of visual, photographic and auroral spectral data, obtained by the Russian astronomer J. Sykora from the Russian-Swedish expedition to Spitsbergen during the 1899–1900 winter season, which are historically significant for auroral studies. These data seem to be the first instrumental observations of auroral spectra in the Arctic and some of the emissions discovered have world priority. The second known photos in the world of aurora from the Arctic and undoubtedly the first ones for geomagnetic latitudes of about 75° in the Spitsbergen Archipelago were obtained. The results of the expedition are discussed from a modern point of view and compared with our knowledge of the 21st century. A description of the equipment and methods that were used by Russian astronomers is presented. Both photographic and spectral devices using registration by photographic plates were used, along with special methods of their development and enhancement. Some statistical analysis was done on the basis of the expedition reports and diaries. This analysis shows that by using Sykora's data it was possible to discover the auroral oval or instantaneous auroral distribution over the polar region. Analysis of photographic samples and sketches of the aurora demonstrate typical auroral form outlines as they are described today. Spectral plates exposed for several hours to auroral lights revealed not only the main auroral emissions, which were well-known at that time, but several other unidentified weak emissions, which were rediscovered and interpreted years later. Keywords. History of geophysics (Atmospheric sciences, instruments and techniques

  13. OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. VI. FURTHER OBSERVATIONS FROM TNG, WHT, OAN, SOAR, AND MAGELLAN TELESCOPES

    Energy Technology Data Exchange (ETDEWEB)

    Álvarez Crespo, N.; Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Milisavljevic, D.; Paggi, A.; Smith, Howard A. [Harvard—Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Landoni, M. [INAF-Osservatorio Astronomico di Brera, Via Emilio Bianchi 46, I-23807 Merate (Italy); Chavushyan, V.; Patiño-Álvarez, V. [Instituto Nacional de Astrofísica, Óptica y Electrónica, Apartado Postal 51-216, 72000 Puebla, México (Mexico); Masetti, N. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129, Bologna (Italy); Jiménez-Bailón, E. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, 22800 Baja California, México (Mexico); Strader, J.; Chomiuk, L. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Katagiri, H.; Kagaya, M. [College of Science, Ibaraki University, 2-1-1, Bunkyo, Mito 310-8512 (Japan); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); D’Abrusco, R. [Department of Physical Sciences, University of Napoli Federico II, via Cinthia 9, I-80126 Napoli (Italy); Ricci, F.; La Franca, F. [Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, I-00146, Roma (Italy); and others

    2016-04-15

    Blazars, one of the most extreme classes of active galaxies, constitute so far the largest known population of γ-ray sources, and their number is continuously growing in the Fermi catalogs. However, in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidates of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition, about one-third of the γ-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower-energy counterpart. Since 2012 we have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 γ-ray blazar candidates from different observing programs we carried out with the Telescopio Nazionale Galileo, William Herschel Telescope, Observatorio Astronómico Nacional, Southern Astrophysical Research Telescope, and Magellan Telescopes. We found that 21 out of 30 sources investigated are BL Lac objects, while the remaining targets are classified as flat-spectrum radio quasars showing the typical broad emission lines of normal quasi-stellar objects. We conclude that our selection of γ-ray blazar candidates based on their multifrequency properties continues to be a successful way to discover potential low-energy counterparts of the Fermi unidentified gamma-ray sources and to confirm the nature of BCUs.

  14. A Sensitive Scheme to Observe Weak Photo-Refraction Effects in Some Nonlinear Optical Crystals Pumped by Ultrashort Optical Pulses

    Institute of Scientific and Technical Information of China (English)

    XU Shi-Xiang; GAO Yan-Xia; CAI Hua; LI Jing-Zhen

    2009-01-01

    We present a sensitive scheme, for the first time to our knowledge, to observe photo-refraction (PR) effects in some nonlinear optical crystals, e.g.β-BBO, LBO and BIBO, pumped by an intense ultrashort laser pulse chain. These quite weak effects are "amplified" by sensitive cw intracavity loss modulation. Our results show that they are repeatable and are dependent on pumping power and wavelength, and their response time ranges from tens of seconds to several minutes. The recorded dynamical transitions between the self-focusing to the self-defocusing (or vice versa) induced by the PR effect may be critically important for us to give more insight into the stability of some cascade nonlinear frequency conversions, e.g. multi-stage optical parametric amplifiers.

  15. Spurious behavior in volcanic records of geomagnetic field reversals

    Science.gov (United States)

    Carlut, Julie; Vella, Jerome; Valet, Jean-Pierre; Soler, Vicente; Legoff, Maxime

    2016-04-01

    Very large directional variations of magnetization have been reported in several lava flows recording a geomagnetic reversal. Such behavior could reflect real geomagnetic changes or be caused by artifacts due to post-emplacement alteration and/or non-ideal magnetic behavior. More recently, a high resolution paleomagnetic record from sediments pleads also for an extremely rapid reversal process during the last reversal. Assuming that the geomagnetic field would have moved by tens of degrees during cooling of moderate thickness lava flows implies brief episodes of rapid changes by a few degrees per day that are difficult to reconcile with the rate of liquid motions at the core surface. Systematical mineralogical bias is a most likely explanation to promote such behavior as recently reconsidered by Coe et al., 2014 for the rapid field changes recorded at Steens Mountain. We resampled three lava flows at La Palma island (Canarias) that are sandwiched between reverse polarity and normal polarity flows associated with the last reversal. The results show an evolution of the magnetization direction from top to bottom. Thermal demagnetization experiments were conducted using different heating and cooling rates. Similarly, continuous demagnetization and measurements. In both cases, we did not notice any remagnetization associated with mineralogical transformations during the experiments. Magnetic grain sizes do not show any correlation with the amplitude of the deviations. Microscopic observations indicate poor exsolution, which could suggests post-cooling thermochemical remagnetization processes.

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

    Science.gov (United States)

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

    2016-07-01

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

  17. Recent developments in the global geomagnetic observatory network

    Science.gov (United States)

    Chulliat, A.

    2011-12-01

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

  18. Space Weather Monitoring for ISS Geomagnetic Storm Studies

    Science.gov (United States)

    Minow, Joseph I.; Parker, Linda Neergaard

    2013-01-01

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

  19. On multifractality of high-latitude geomagnetic fluctuations

    Directory of Open Access Journals (Sweden)

    Z. Vörös

    Full Text Available In order to contribute to the understanding of solar wind-magnetosphere interactions the multifractal scaling properties of high-latitude geomagnetic fluctuations observed at the Thule observatory have been studied. Using the local observatory data and the present experimental knowledge only it seems hard to characterize directly the, presumably intermittent, mesoscale energy accumulation and dissipation processes taking place at the magnetotail, auroral region, etc. Instead a positive probability measure, describing the accumulated local geomagnetic signal energy content at the given time scales has been introduced and its scaling properties have been studied. There is evidence for the multifractal nature of the so defined intermittent field ε, a result obtained by using the recently introduced technique of large deviation multifractal spectra. This technique allows us to describe the geomagnetic fluctuations locally in time by means of singularity exponents α, which represent a generalization of the local degree of differentiability and characterize the power-law scaling dependence of the introduced measure on resolution. A global description of the geomagnetic fluctuations is insured by the spectrum of exponents f(α which represents a rate function quantifying the deviations of the observed singularities α from the expected value. The results show that there exists a multifractal counterpart of the previously reported spectral break and different types of f(α spectra describe the fluctuations in direct dissipation or loading-unloading regimes of the solar wind-magnetosphere interaction. On the time scale of substorms and storms the multi-fractal structure of the loading-unloading mode fluctuations seems to be analogous to the simple multiplicative P-model, while the f(α spectra in direct dissipation regime are close but not equal to the features of a uniform distribution. Larger deviations from the multiplicative

  20. Stochastic forecasting of the geomagnetic field from the COV-OBS.x1 geomagnetic field model, and candidate models for IGRF-12

    DEFF Research Database (Denmark)

    Gillet, Nicolas; Barrois, Olivier; Finlay, Chris

    2015-01-01

    filter algorithm. We show that the envelope of forecasts includes the observed secular variation of the geomagnetic field over 5-year intervals, even in the case of rapid changes. In a purpose of testing hypotheses about the core dynamics, this prototype method could be implemented to build the ‘state......We present the geomagnetic field model COV-OBS.x1, covering 1840 to 2020, from which have been derived candidate models for the IGRF-12. Towards the most recent epochs, it is primarily constrained by first differences of observatory annual means and measurements from the Oersted, Champ, and Swarm...... the ‘observations’ uncertainties in data assimilation schemes for the study of the outer core dynamics.We also present and illustrate a stochastic algorithm designed to forecast the geomagnetic field. The radial field at the outer core surface is advected by core motions governed by an auto-regressive process...

  1. Bio-optical water quality dynamics observed from MERIS in Pensacola Bay, Florida

    Science.gov (United States)

    Observed bio-optical water quality data collected from 2009 to 2011 in Pensacola Bay, Florida were used to develop empirical remote sensing retrieval algorithms for chlorophyll a (Chla), colored dissolved organic matter (CDOM), and suspended particulate matter (SPM). Time-series ...

  2. Observer-Based Control Techniques for the LBT Adaptive Optics under Telescope Vibrations

    NARCIS (Netherlands)

    Agapito, Guido; Quirós-Pacheco, Fernando; Tesi, Pietro; Riccardi, Armando; Esposito, Simone

    2011-01-01

    This paper addresses the application of observer-based control techniques for the adaptive optics system of the LBT telescope. In such a context, attention is focused on the use of Kalman and H∞ filters to estimate the temporal evolution of phase perturbations due to the atmospheric turbulence and

  3. Optical observations of Dwingeloo 1, a nearby barred spiral galaxy behind the Milky Way

    NARCIS (Netherlands)

    Loan, AJ; Maddox, SJ; Lahav, O; Balcells, M; KraanKorteweg, RC; Assendorp, R; Almoznino, E; Brosch, N; Goldberg, E; Ofek, EO

    1996-01-01

    We present new optical observations of the nearby barred spiral galaxy Dwingeloo 1 (Dw1) obtained with the Isaac Newton, William Herschel and Wise telescopes. Dw1 lies at Galactic coordinates (l=138.degrees 52, b=-0.degrees 11) and it is heavily obscured by dust and gas in the Milky Way. We infer th

  4. Observations and modeling of fog by cloud radar and optical sensors

    NARCIS (Netherlands)

    Li, Y.; Hoogeboom, P.; Russchenberg, H.

    2014-01-01

    Fog is a significant factor affecting the public traffic because visibility is reduced to a large extent. Therefore the determination of optical visibility in fog from radar instruments has received much interest. To observe fog with radar, high frequency bands (millimeter waves) have the best

  5. Aerosol Optical Depth as Observed by the Mars Science Laboratory REMS UV Photodiodes

    Science.gov (United States)

    Smith, M. D.; Zorzano, M.-P.; Lemmon, M.; Martin-Torres, J.; Mendaza de Cal, T.

    2017-01-01

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately two Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270deg, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time. A full description of these observations, the retrieval algorithm, and the results can be found in Smith et al. (2016).

  6. Observations and modeling of fog by cloud radar and optical sensors

    NARCIS (Netherlands)

    Li, Y.; Hoogeboom, P.; Russchenberg, H.

    2014-01-01

    Fog is a significant factor affecting the public traffic because visibility is reduced to a large extent. Therefore the determination of optical visibility in fog from radar instruments has received much interest. To observe fog with radar, high frequency bands (millimeter waves) have the best optio

  7. Bio-optical water quality dynamics observed from MERIS in Pensacola Bay, Florida

    Science.gov (United States)

    Observed bio-optical water quality data collected from 2009 to 2011 in Pensacola Bay, Florida were used to develop empirical remote sensing retrieval algorithms for chlorophyll a (Chla), colored dissolved organic matter (CDOM), and suspended particulate matter (SPM). Time-series ...

  8. Development of a Reduction Algorithm of GEO Satellite Optical Observation Data for Optical Wide Field Patrol (OWL)

    Science.gov (United States)

    Park, Sun-youp; Choi, Jin; Jo, Jung Hyun; Son, Ju Young; Park, Yung-Sik; Yim, Hong-Suh; Moon, Hong-Kyu; Bae, Young-Ho; Choi, Young-Jun; Park, Jang-Hyun

    2015-09-01

    An algorithm to automatically extract coordinate and time information from optical observation data of geostationary orbit satellites (GEO satellites) or geosynchronous orbit satellites (GOS satellites) is developed. The optical wide-field patrol system is capable of automatic observation using a pre-arranged schedule. Therefore, if this type of automatic analysis algorithm is available, daily unmanned monitoring of GEO satellites can be possible. For data acquisition for development, the COMS1 satellite was observed with 1-s exposure time and 1-m interval. The images were grouped and processed in terms of ¡°action¡±, and each action was composed of six or nine successive images. First, a reference image with the best quality in one action was selected. Next, the rest of the images in the action were geometrically transformed to fit in the horizontal coordinate system (expressed in azimuthal angle and elevation) of the reference image. Then, these images were median-combined to retain only the possible non-moving GEO candidates. By reverting the coordinate transformation of the positions of these GEO satellite candidates, the final coordinates could be calculated.

  9. On Geomagnetism and Paleomagnetism I

    Science.gov (United States)

    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.

  10. Deep optical observations of the γ-ray pulsar J0357+3205

    Science.gov (United States)

    Kirichenko, A.; Danilenko, A.; Shibanov, Yu.; Shternin, P.; Zharikov, S.; Zyuzin, D.

    2014-04-01

    Context. A middle-aged radio-quiet pulsar J0357+3205 was discovered in gamma rays with Fermi and later in X-rays with Chandra and XMM-Newton observatories. It produces an unusual thermally emitting pulsar wind nebula that is observed in X-rays. Aims: Deep optical observations were obtained to search for the pulsar optical counterpart and its nebula using the Gran Telescopio Canarias (GTC). Methods: The direct imaging mode in the Sloan g' band was used. Archival X-ray data were reanalysed and compared with the optical data. Results: No pulsar optical counterpart was detected down to g'≥slant 28.1m. No pulsar nebula was identified in the optical either. We confirm early results that the X-ray spectrum of the pulsar consists of a nonthermal power-law component of the pulsar magnetospheric origin dominating at high energies and a soft thermal component from the neutron star surface. Using magnetised, partially ionised hydrogen atmosphere models in X-ray spectral fits, we found that the thermal component can come from the entire surface of the cooling neutron star with a temperature of 36+8-6 eV, making it one of the coldest among cooling neutron stars known. The surface temperature agrees with the standard neutron star cooling scenario. The optical upper limit does not put any additional constraints on the thermal component, however it does imply a strong spectral break for the nonthermal component between the optical and X-rays as is observed in other middle-aged pulsars. Conclusions: The thermal emission from the entire surface of the neutron star very likely dominates the nonthermal emission in the UV range. Observations of PSR J0357+3205 in this range are promising to put more stringent constraints on its thermal properties. Based on observations made with the Gran Telescopio Canarias (GTC), instaled in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma under Programme GTC3-12BMEX

  11. Deep optical observations of the gamma-ray pulsar J0357+3205

    CERN Document Server

    Kirichenko, Aida; Shibanov, Yury; Shternin, Peter; Zharikov, Sergey; Zyuzin, Dmitry

    2014-01-01

    A middle-aged radio-quiet pulsar J0357+3205 was discovered in gamma-rays with $Fermi$ and later in X-rays with $Chandra$ and $XMM$-$Newton$ observatories. It produces an unusual thermally-emitting pulsar wind nebula observed in X-rays. Deep optical observations were obtained to search for the pulsar optical counterpart and its nebula using the Gran Telescopio Canarias (GTC). The direct imaging mode in the Sloan $g'$ band was used. Archival X-ray data were reanalysed and compared with the optical data. No pulsar optical counterpart was detected down to $g'\\geq~28_{\\cdotp}^{\\text{m}}1$. No pulsar nebula was either identified in the optical. We confirm early results that the X-ray spectrum of the pulsar consists of a nonthermal power-law component of the pulsar magnetospheric origin dominating at high energies and a soft thermal component from the neutron star surface. Using magnetised partially ionised hydrogen atmosphere models in X-ray spectral fits we found that the thermal component can come from entire sur...

  12. Observation of Shot Noise Suppression at Optical Wavelengths in a Relativistic Electron Beam

    Energy Technology Data Exchange (ETDEWEB)

    Ratner, Daniel; Stupakov, Gennady; /SLAC

    2012-06-19

    Control of collective properties of relativistic particles is increasingly important in modern accelerators. In particular, shot noise affects accelerator performance by driving instabilities or by competing with coherent processes. We present experimental observations of shot noise suppression in a relativistic beam at the Linac Coherent Light Source. By adjusting the dispersive strength of a chicane, we observe a decrease in the optical transition radiation emitted from a downstream foil. We show agreement between the experimental results, theoretical models, and 3D particle simulations.

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

    Directory of Open Access Journals (Sweden)

    D. M. Willis

    2009-01-01

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

  14. Geomagnetism during solar cycle 23: Characteristics

    Directory of Open Access Journals (Sweden)

    Jean-Louis Zerbo

    2013-05-01

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

  15. Geomagnetism during solar cycle 23: Characteristics.

    Science.gov (United States)

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

    2013-05-01

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

  16. Bayesian modeling of perceived surface slant from actively-generated and passively-observed optic flow.

    Directory of Open Access Journals (Sweden)

    Corrado Caudek

    Full Text Available We measured perceived depth from the optic flow (a when showing a stationary physical or virtual object to observers who moved their head at a normal or slower speed, and (b when simulating the same optic flow on a computer and presenting it to stationary observers. Our results show that perceived surface slant is systematically distorted, for both the active and the passive viewing of physical or virtual surfaces. These distortions are modulated by head translation speed, with perceived slant increasing directly with the local velocity gradient of the optic flow. This empirical result allows us to determine the relative merits of two alternative approaches aimed at explaining perceived surface slant in active vision: an "inverse optics" model that takes head motion information into account, and a probabilistic model that ignores extra-retinal signals. We compare these two approaches within the framework of the bayesian theory. The "inverse optics" bayesian model produces veridical slant estimates if the optic flow and the head translation velocity are measured with no error; because of the influence of a "prior" for flatness, the slant estimates become systematically biased as the measurement errors increase. The bayesian model, which ignores the observer's motion, always produces distorted estimates of surface slant. Interestingly, the predictions of this second model, not those of the first one, are consistent with our empirical findings. The present results suggest that (a in active vision perceived surface slant may be the product of probabilistic processes which do not guarantee the correct solution, and (b extra-retinal signals may be mainly used for a better measurement of retinal information.

  17. Observations of artificial and natural optical emissions at the HAARP facility

    Directory of Open Access Journals (Sweden)

    T. Pedersen

    2008-05-01

    Full Text Available Extensive optical observations have been carried out at the High Frequency Active Auroral Research Program (HAARP ionospheric heating facility since it began operations in 1999. A number of modern optical diagnostic instruments are hosted at remote sites as well as the main transmitter facility, which has recently been expanded from the initial 960 kW prototype configuration to its full 3.6 MW design capability. Upgrades to optical diagnostics have allowed a number of interesting new observations to be made at the 960 kW power level since 2004. Systematic beam-swinging experiments generating quantifiable levels of optical emission at various regions in the sky for the first time clearly show that emission intensity is very sensitive to distance from the magnetic zenith, and drops off rapidly at about 15° zenith angle in directions other than magnetic south. High temporal resolution measurements of emissions in the 557.7 nm green line at start-up and in short transmitter pulses demonstrate that localized irregularities are preferentially excited in the initial seconds of heating, with evolution into a more homogenous spot occurring over a period of about 1 min. High-quality emission altitude profiles at both 630.0 and 557.7 nm have recently been isolated from side-looking data, spanning an altitude extent of over 200 km, which has allowed determination of the effective lifetime of O (1D over an unprecedented altitude range. An innovative automated remote imager network utilizing low-cost mirror optics has been designed and deployed to make such measurements routinely. Observations of natural optical emissions at the site have revealed the common presence of highly structured but faint co-rotating subauroral precipitation that acts to suppress excitation of artificial F region optical emissions in areas of active precipitation. The observed spatial modulation of artificial optical emissions by structured precipitation is consistent

  18. First Gravitational-Wave Burst GW150914: Part II. MASTER Optical Follow-Up Observations

    CERN Document Server

    Lipunov, V M; Gorbovskoy, E; Tiurina, N; Balanutsa, P; Kuznetsov, A; Vladimirov, V; Vlasenko, D; Gorbunov, I; Chazov, V; Kuvshinov, D; Gabovich, A; Buckley, D A H; Potter, S B; Kniazev, A; Crawford, S; Lopez, R Rebolo; Ricart, M Serra; Israelian, G; Lodieu, N; Gress, O A; Budnev, N M; Ivanov, K I; Poleschuk, V; Yazev, S; Tlatov, A; Senik, V; Dormidontov, D; Parkhomenko, A; Yurkov, V; Sergienko, Yu; Podesta, R; Levato, H; Lopez, C; Saffe, C; Mallamaci, C

    2016-01-01

    The Advanced LIGO observatory recently reported the first direct detection of gravitational waves predicted by Einstein (1916). We report on the first optical observations of the Gravitational Wave (GW) source GW150914 error region with the Global MASTER Robotic Net. We detected several optical transients, which proved to be unconnected with the GW event. Our result is consistent with the assumption that gravitational waves were produced by a binary black hole merger. The detection of the event confirmed the main prediction of the population synthesis performed with the "Scenario Machine" formulated in Lipunov1997b.

  19. Review on optical constants of Titan aerosols: Experimental results and modeling/observational data

    Science.gov (United States)

    Brassé, Coralie; Muñoz, Olga; Coll, Patrice; Raulin, François

    2014-05-01

    During the last years many studies have been performed to improve the experimental database of optical constants of Titan aerosols. Indeed, the determination of the optical constants of these particles is essential to quantify their capacity to absorb and to scatter solar radiation, and thus to evaluate their role on Titan's radiative balance and climate. The study of optical properties is also crucial to analyze and to better interpret many of Titan's observational data, in particular those acquired during the Cassini-Huygens mission. One way to determine Titan aerosols optical constant is to measure the optical constants of analogues of Titan complex organic material synthesized in the laboratory, usually named Titan's tholins (Sagan and Khare, 1979). But the optical constants depend on the chemical composition, the size and the shape of particles (Raulin et al., 2012). Those three parameters result from the experimental conditions such as energy source, gas mixing ratio, gas pressure, flow rate and irradiation time (Cable et al., 2012). Besides the determination of the refractive index in the laboratory, there are others methods using theoretical models or observational data. Nevertheless, theoretical models are based on laboratory data or/and observational data. The visible - near infrared spectral region of optical constants has been widely studied with laboratory analogues. Comparison of the obtained results suggest that tholins synthesized by Tran et al. (2003) and Majhoub et al. (2012) are the best representative of Titan aerosols with regards to their refractive indexes in this spectral region. The mid-infrared spectral range has been studied only by Imanaka et al. (2012) and slightly by Tran et al. (2003). In that spectral range, Titan tholins do not exhibit the features displayed by Kim and Courtin (2013) from Titan's observations. For spectral region of wavelengths smaller than 0.20µm or higher than 25µm, only the data from Khare et al. (1984) are

  20. Aerosol optical depth as observed by the Mars Science Laboratory REMS UV photodiodes

    Science.gov (United States)

    Smith, Michael D.; Zorzano, María-Paz; Lemmon, Mark; Martín-Torres, Javier; Mendaza de Cal, Teresa

    2016-12-01

    Systematic observations taken by the REMS UV photodiodes on a daily basis throughout the landed Mars Science Laboratory mission provide a highly useful tool for characterizing aerosols above Gale Crater. Radiative transfer modeling is used to model the approximately 1.75 Mars Years of observations taken to date taking into account multiple scattering from aerosols and the extended field of view of the REMS UV photodiodes. The retrievals show in detail the annual cycle of aerosol optical depth, which is punctuated with numerous short timescale events of increased optical depth. Dust deposition onto the photodiodes is accounted for by comparison with aerosol optical depth derived from direct imaging of the Sun by Mastcam. The effect of dust on the photodiodes is noticeable, but does not dominate the signal. Cleaning of dust from the photodiodes was observed in the season around Ls=270°, but not during other seasons. Systematic deviations in the residuals from the retrieval fit are indicative of changes in aerosol effective particle size, with larger particles present during periods of increased optical depth. This seasonal dependence of aerosol particle size is expected as dust activity injects larger particles into the air, while larger aerosols settle out of the atmosphere more quickly leading to a smaller average particle size over time.

  1. Observation and measurement of interaction-induced dispersive optical nonlinearities in an ensemble of cold rydberg atoms

    DEFF Research Database (Denmark)

    Parigi, V.; Bimbard, E.; Stanojevic, J.

    2012-01-01

    We observe and measure dispersive optical nonlinearities in an ensemble of cold Rydberg atoms placed inside an optical cavity. The experimental results are in agreement with a simple model where the optical nonlinearities are due to the progressive appearance of a Rydberg blockaded volume within ...

  2. Observation and measurement of interaction-induced dispersive optical nonlinearities in an ensemble of cold Rydberg atoms.

    Science.gov (United States)

    Parigi, Valentina; Bimbard, Erwan; Stanojevic, Jovica; Hilliard, Andrew J; Nogrette, Florence; Tualle-Brouri, Rosa; Ourjoumtsev, Alexei; Grangier, Philippe

    2012-12-07

    We observe and measure dispersive optical nonlinearities in an ensemble of cold Rydberg atoms placed inside an optical cavity. The experimental results are in agreement with a simple model where the optical nonlinearities are due to the progressive appearance of a Rydberg blockaded volume within the medium. The measurements allow a direct estimation of the "blockaded fraction" of atoms within the atomic ensemble.

  3. Bats Use Geomagnetic Field: Behavior and Mechanism

    Science.gov (United States)

    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

  4. Effect of a huge crustal conductivity anomaly on the H-component of geomagnetic variations recorded in central South America

    Science.gov (United States)

    Padilha, Antonio L.; Alves, Livia R.; Silva, Graziela B. D.; Espinosa, Karen V.

    2017-04-01

    We describe here an analysis of the H-component of the geomagnetic field recorded in several temporary stations operating simultaneously in the central-eastern region of Brazil during nighttime pulsation events in 1994 and the sudden commencement of the St. Patrick's Day magnetic storm in 2015. A significant amplification in the amplitude of the geomagnetic variations is consistently observed in one of these stations. Magnetovariational analysis indicates that the amplification factor is period dependent with maximum amplitude around 100 s. Integrated magnetotelluric (MT) and geomagnetic depth soundings (GDS) have shown that this station is positioned just over a huge 1200-km-long crustal conductor (estimated bulk conductivity greater than 1 S/m). We propose that the anomalous signature of the geomagnetic field at this station is due to the high reflection coefficient of the incident electromagnetic wave at the interface with the very good conductor and by skin effects damping the electromagnetic wave in the conducting layers overlying the conductor. There are some indication from the GDS data that the conductor extends southward beneath the sediments of the Pantanal Basin. In this region is being planned the installation of a new geomagnetic observatory, but its preliminary data suggest anomalous geomagnetic variations. We understand that a detailed MT survey must be carried out around the chosen observatory site to evaluate the possible influence of induced currents on the local geomagnetic field.[Figure not available: see fulltext.

  5. Data Fusion Based on Optical Technology for Observation of Human Manipulation

    Science.gov (United States)

    Falco, Pietro; De Maria, Giuseppe; Natale, Ciro; Pirozzi, Salvatore

    2012-01-01

    The adoption of human observation is becoming more and more frequent within imitation learning and programming by demonstration approaches (PbD) to robot programming. For robotic systems equipped with anthropomorphic hands, the observation phase is very challenging and no ultimate solution exists. This work proposes a novel mechatronic approach to the observation of human hand motion during manipulation tasks. The strategy is based on the combined use of an optical motion capture system and a low-cost data glove equipped with novel joint angle sensors, based on optoelectronic technology. The combination of the two information sources is obtained through a sensor fusion algorithm based on the extended Kalman filter (EKF) suitably modified to tackle the problem of marker occlusions, typical of optical motion capture systems. This approach requires a kinematic model of the human hand. Another key contribution of this work is a new method to calibrate this model.

  6. First results from the Burst Observer and Optical Transient Exploring System station 1 (BOOTES-1)

    Science.gov (United States)

    Castro-Tirado, A. J.; Soldán, J.; Bernas, M.; Páta, P.; Hudec, R.; Sanguino, T. M.; de La Morena, B.; Berná, J. A.; de Ugarte, A.; Gorosabel, J.; Más-Hesse, J. M.; Giménez, A.

    2000-09-01

    The Burst Observer and Optical Transient Exploring System (BOOTES) is considered as a part of the preparations for ESA's INTEGRAL satellite, and is currently being developed in Spain, in collaboration with two Czech institutions. It makes use of two sets of wide-field cameras, 240 km apart, and two robotic 0.3-m telescopes. The first observing station (BOOTES-1) is located in Huelva (Spain) and the first light was obtained in July 1998. During the test phase, it has provided rapid follow-up observations with the wide-field cameras for 19 GRBs detected by BATSE aboard CGRO, and narrow-field imaging for 6 bursts. Limiting magnitudes for any GRB optical afterglow are I~13 and R~16.5, a few minutes after the events. .

  7. 11 years observing with OMC, the Optical Monitoring Camera on board the INTEGRAL satellite

    Science.gov (United States)

    Alfonso-Garzón, J.; Domingo, A.; Mas-Hesse, J. M.

    2015-05-01

    The Optical Monitoring Camera (OMC) on board the INTEGRAL observatory provides photometry in the Johnson V band, complementing the high-energy instruments which take images and spectra in hard X-rays and soft gamma--rays. After 11 years of mission operations, it has been possible to compile optical photometric light curves for a very large number of objects, with observational time spans of more than a decade and with a stable and consistent photometric calibration. In this contribution, we present a summary of some of the most interesting scientific results reached with INTEGRAL/OMC data, including the compilation of a catalogue of optically variable sources, some results on the analysis of temporal correlations between different energy ranges and the OMC monitoring of the supernova SN 2014J.

  8. The optical properties of equatorial cirrus in the pilot radiation observation experiment

    Energy Technology Data Exchange (ETDEWEB)

    Platt, C.M.R.; Young, S.A.; Manson, P.; Patterson, G.R. [CSIRO, Victoria (Australia)] [and others

    1996-04-01

    The development of a sensitive filter radiometer for the Atmospheric Radiation Measurement (ARM) Program has been reported. The aim was to develop a reliable and fast instrument that could be used alongside a lidar to obtain near realtime optical properties of clouds, particularly high ice clouds, as they drifted over an ARM Cloud and Radiation Testbed (CART) site allowing calculation of the radiation divergence in the atmosphere over the site. Obtaining cloud optical properties by the lidar/radiometer, or LIRAD, method was described by Platt et al.; the latter paper also describes a year`s data on mid-latitude cirrus. The optical properties of equatorial cirrus (i.e., cirrus within a few degrees of the equator) have hardly been studied at all. The same is true of tropical cirrus, although a few observations have been reported by Davis and Platt et al.This paper describes obersvations performed on cirrus clouds, analysis methods used, and results.

  9. Observation of Parity-Time Symmetry in Optically Induced Atomic Lattices

    CERN Document Server

    Zhang, Zhaoyang; Sheng, Jiteng; Yang, Liu; Miri, Mohammad-Ali; Christodoulides, Demetrios N; He, Bing; Zhang, Yanpeng; Xiao, Min

    2016-01-01

    A wide class of non-Hermitian Hamiltonians can possess entirely real eigenvalues when they have parity-time (PT) symmetric potentials. Due to their unusual properties, this family of non-Hermitian systems has recently attracted considerable attention in diverse areas of physics, especially in coupled gain-loss waveguides and optical lattices. Given that multi-level atoms can be quite efficient in judiciously synthesizing refractive index profiles, schemes based on atomic coherence have been recently proposed to realize optical potentials with PT-symmetric properties. Here, we experimentally demonstrate for the first time PT-symmetric optical lattices in a coherently-prepared four-level N-type atomic system. By appropriately tuning the pertinent atomic parameters, the onset of PT symmetry breaking is observed through measuring an abrupt phase-shift jump. The experimental realization of such readily reconfigurable and effectively controllable PT-symmetric periodic lattice structures sets a new stage for further...

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

    Directory of Open Access Journals (Sweden)

    C. Oprea

    2013-08-01

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

  11. Contribution of solar radiation and geomagnetic activity to global structure of 27-day variation of ionosphere

    Science.gov (United States)

    Yao, Yibin; Zhai, Changzhi; Kong, Jian; Liu, Lei

    2017-04-01

    Twenty-seven-day variation caused by solar rotation is one of the main periodic effects of solar radiation influence on the ionosphere, and there have been many studies on this periodicity using peak electron density N_{mF2} and solar radio flux index F10.7. In this paper, the global electron content (GEC) and observation of Solar EUV Monitor (SEM) represent the whole ionosphere and solar EUV flux, respectively, to investigate the 27-day variation. The 27-day period components of indices (GEC_{27}, SEM_{27}, F10.7_{27}, Ap_{27}) are obtained using Chebyshev band-pass filter. The comparison of regression results indicates that the index SEM has higher coherence than F10.7 with 27-day variation of the ionosphere. The regression coefficients of SEM_{27 } varied from 0.6 to 1.4 and the coefficients of Ap_{27} varied from - 0.6 to 0.3, which suggests that EUV radiation seasonal variations are the primary driver for the 27-day variations of the ionosphere for most periods. TEC map grid points on three meridians where IGS stations are dense are selected for regression, and the results show that the contribution of solar EUV radiation is positive at all geomagnetic latitudes and larger than geomagnetic activity in most latitudes. The contribution of geomagnetic activity is negative at high geomagnetic latitude, increasing with decreasing geomagnetic latitudes, and positive at low geomagnetic latitudes. The global structure of 27-day variation of ionosphere is presented and demonstrates that there are two zonal anomaly regions along with the geomagnetic latitudes lines and two peaks in the north of Southeast Asia and the Middle Pacific where TEC_{27} magnitude values are notably larger than elsewhere along zonal anomaly regions.

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

    Science.gov (United States)

    Love, Jeffrey J.

    2009-01-01

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

  13. F2 region response to geomagnetic disturbances across Indian latitudes: O(1S) dayglow emission

    Science.gov (United States)

    Upadhayaya, A. K.; Gupta, Sumedha; Brahmanandam, P. S.

    2016-03-01

    The morphology of ionospheric storms has been investigated across equatorial and low latitudes of Indian region. The deviation in F2 region characteristic parameters (foF2 and h'F) along with modeled green line dayglow emission intensities is examined at equatorial station Thiruvananthapuram (8.5°N, 76.8°E, 0.63°S geomagnetic latitude) and low-latitude station Delhi (28.6°N, 77.2°E,19.2°N geomagnetic latitude) during five geomagnetic storm events. Both positive and negative phases have been noticed in this study. The positive storm phase over equatorial station is found to be more frequent, while the drop in ionization in most of the cases was observed at low-latitude station. It is concluded that the reaction as seen at different ionospheric stations may be quite different during the same storm depending on both the geographic and geomagnetic coordinates of the station, storm intensity, and the storm onset time. Modulation in the F2 layer critical frequency at low and equatorial stations during geomagnetic disturbance of 20-23 November 2003 was caused by the storm-induced changes in O/N2. It is also found that International Reference Ionosphere 2012 model predicts the F2 layer characteristic (foF2 and h'F) parameters at both the low and equatorial stations during disturbed days quite reasonably. A simulative approach in GLOW model developed by Solomon is further used to estimate the changes in the volume emission rate of green line dayglow emission under quiet and strong geomagnetic conditions. It is found that the O(1S) dayglow thermospheric emission peak responds to varying geomagnetic conditions.

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

    Science.gov (United States)

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

    2014-05-01

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

  15. The optical luminosity function of gamma-ray bursts deduced from ROTSE-III observations

    Energy Technology Data Exchange (ETDEWEB)

    Cui, X. H.; Wu, X. F.; Wei, J. J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Yuan, F. [Research School of Astronomy and Astrophysics, The Australian National University, Weston Creek, ACT 2611 (Australia); Zheng, W. K. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Liang, E. W. [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Akerlof, C. W.; McKay, T. A. [Department of Physics, University of Michigan, Ann Arbor, MI 48109 (United States); Ashley, M. C. B. [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Flewelling, H. A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Göǧüş, E. [Sabancı University, Orhanlı-Tuzla, 34956 İstanbul (Turkey); Güver, T. [Department of Astronomy and Space Sciences, Istanbul University Science Faculty, 34119 Istanbul (Turkey); Kızıloǧlu, Ü. [Middle East Technical University, 06531 Ankara (Turkey); Pandey, S. B. [ARIES, Manora Peak, Nainital 263129, Uttarakhand (India); Rykoff, E. S. [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Rujopakarn, W. [Department of Physics, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Pathumwan, Bangkok 10330 (Thailand); Schaefer, B. E. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Wheeler, J. C. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Yost, S. A., E-mail: xhcui@bao.ac.cn, E-mail: xfwu@pmo.ac.cn, E-mail: jjwei@pmo.ac.cn, E-mail: fang.yuan@anu.edu.au, E-mail: zwk@astro.berkeley.edu, E-mail: lew@gxu.edu.cn [Department of Physics, College of St. Benedict, St. John' s University, Collegeville, MN 56321 (United States)

    2014-11-10

    We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs) and those with upper limits (40 GRBs). We derive R-band fluxes for these two sub-samples 100 s after the onset of the burst. The optical LFs at 100 s are fitted by assuming that the co-moving GRB rate traces the star formation rate. While fitting the optical LFs using Monte Carlo simulations, we take into account the detection function of ROTSE-III. We find that the cumulative distribution of optical emission at 100 s is well described by an exponential rise and power-law decay, a broken power law,and Schechter LFs. A single power-law (SPL) LF, on the other hand, is ruled out with high confidence.

  16. The Optical Luminosity Function of Gamma-ray Bursts deduced from ROTSE-III Observations

    CERN Document Server

    Cui, X H; Wei, J J; Yuan, F; Zheng, W K; Liang, E W; Akerlof, C W; Ashley, M C B; Flewelling, H A; Gogus, E; Guver, T; Kiziloglu, U; McKay, T A; Pandey, S B; Rykoff, E S; Rujopakarn, W; Schaefer, B E; Wheeler, J C; Yost, S A

    2014-01-01

    We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs), and those with upper limits (40 GRBs). The $R$ band fluxes 100s after the onset of the burst for these two sub-samples are derived. The optical LFs at 100s are fitted by assuming that the co-moving GRB rate traces the star-formation rate. The detection function of ROTSE-III is taken into account during the fitting of the optical LFs by using Monte Carlo simulations. We find that the cumulative distribution of optical emission at 100s is well-described with an exponential rise and power-law decay (ERPLD), broken power-law (BPL), and Schechter LFs. A single power-law (SPL) LF, on the other hand, is ruled out with high confidence.

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

    Science.gov (United States)

    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.

  18. Infrared response of the thermosphere-ionosphere system to geomagnetic storms

    Science.gov (United States)

    Thayer, J. P.; Mlynczak, M. G.; Hunt, L. A.; Russell, J. M., III

    2015-12-01

    For 14 years the SABER instrument on the NASA TIMED satellite has been observing the radiative cooling of the thermosphere-ionosphere system associated with infrared emission by nitric oxide (NO) and carbon dioxide (CO2). From these observations a very clear picture of fundamental processes that control the thermal structure above 100 km has emerged. The radiative cooling is modulated by variations in solar UV irradiance and geomagnetic effects. A pronounced solar cycle variation in both NO and CO2 cooling is observed, and CO2 cooling dominates during solar minimum. Radiative cooling in the current maximum peaked in December 2014, nine months after the sunspot peak. On average, solar ultraviolet irradiance provides about 70% of the energy that results in cooling by NO and the remaining 30% arises from geomagnetic processes. The relative roles of irradiance and geomagnetism vary strongly over a solar cycle. Of particular interest are the large, short-term increases in radiative cooling associated with intense geomagnetic storms. The large energy deposition heats the atmosphere and the infrared cooling increases non-linearly, helping the atmosphere to shed the storm energy and rapidly return to pre-storm conditions. This "natural thermostat" effect of infrared radiation will be shown in detail in this talk, as a function of latitude and altitude for a number of different geomagnetic storms. The relative roles of radiative cooling by NO and CO2 will also be investigated, to see if there is any storm-dependent preference. Finally, the sensitivity of the NO cooling to geomagnetic processes suggests that near real time observations of NO emission may serve as a forecasting tool for space weather. Increases in NO infrared emissions are associated with energy deposition and heating of the atmosphere. Observations of NO emission may then identify regions in which atmospheric drag is increasing, and thus may be a tool for now casting of drag for space operations.

  19. Geomagnetically trapped, albedo and solar energetic particles: trajectory analysis and flux reconstruction with PAMELA

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N

    2016-01-01

    The PAMELA satellite experiment is providing comprehensive observations of the interplanetary and magnetospheric radiation in the near-Earth environment. Thanks to its identification capabilities and the semi-polar orbit, PAMELA is able to precisely measure the energetic spectra and the angular distributions of the different cosmic-ray populations over a wide latitude region, including geomagnetically trapped and albedo particles. Its observations comprise the solar energetic particle events between solar cycles 23 and 24, and the geomagnetic cutoff variations during magnetospheric storms. PAMELA's measurements are supported by an accurate analysis of particle trajectories in the Earth's magnetosphere based on a realistic geomagnetic field modeling, which allows the classification of particle populations of different origin and the investigation of the asymptotic directions of arrival.

  20. Geomagnetic storms can trigger stroke: evidence from 6 large population-based studies in Europe and Australasia.

    Science.gov (United States)

    Feigin, Valery L; Parmar, Priya G; Barker-Collo, Suzanne; Bennett, Derrick A; Anderson, Craig S; Thrift, Amanda G; Stegmayr, Birgitta; Rothwell, Peter M; Giroud, Maurice; Bejot, Yannick; Carvil, Phillip; Krishnamurthi, Rita; Kasabov, Nikola

    2014-06-01

    Although the research linking cardiovascular disorders to geomagnetic activity is accumulating, robust evidence for the impact of geomagnetic activity on stroke occurrence is limited and controversial. We used a time-stratified case-crossover study design to analyze individual participant and daily geomagnetic activity (as measured by Ap Index) data from several large population-based stroke incidence studies (with information on 11 453 patients with stroke collected during 16 031 764 person-years of observation) in New Zealand, Australia, United Kingdom, France, and Sweden conducted between 1981 and 2004. Hazard ratios and corresponding 95% confidence intervals (CIs) were calculated. Overall, geomagnetic storms (Ap Index 60+) were associated with 19% increase in the risk of stroke occurrence (95% CI, 11%-27%). The triggering effect of geomagnetic storms was most evident across the combined group of all strokes in those aged 50%: moderate geomagnetic storms (60-99 Ap Index) were associated with a 27% (95% CI, 8%-48%) increased risk of stroke occurrence, strong geomagnetic storms (100-149 Ap Index) with a 52% (95% CI, 19%-92%) increased risk, and severe/extreme geomagnetic storms (Ap Index 150+) with a 52% (95% CI, 19%-94%) increased risk (test for trend, Pstorms are associated with increased risk of stroke and should be considered along with other established risk factors. Our findings provide a framework to advance stroke prevention through future investigation of the contribution of geomagnetic factors to the risk of stroke occurrence and pathogenesis. © 2014 American Heart Association, Inc.

  1. Modelling and Observation of Mineral Dust Optical Properties over Central Europe

    Science.gov (United States)

    Chilinski, Michał T.; Markowicz, Krzysztof M.; Zawadzka, Olga; Stachlewska, Iwona S.; Kumala, Wojciech; Petelski, Tomasz; Makuch, Przemysław; Westphal, Douglas L.; Zagajewski, Bogdan

    2016-12-01

    This paper is focused on Saharan dust transport to Central Europe/Poland; we compare properties of atmospheric Saharan dust using data from NAAPS, MACC, AERONET as well as observations obtained during HyMountEcos campaign in June 2012. Ten years of dust climatology shows that long-range transport of Saharan dust to Central Europe is mostly during spring and summer. HYSPLIT back-trajectories indicate airmass transport mainly in November, but it does not agree with modeled maxima of dust optical depth. NAAPS model shows maximum of dust optical depth ( 0.04-0.05, 550 nm) in April-May, but the MACC modeled peak is broader ( 0.04). During occurrence of mineral dust over Central-Europe for 14% (NAAPS) / 12% (MACC) of days dust optical depths are above 0.05 and during 4% (NAAPS) / 2.5% (MACC) of days dust optical depths exceed 0.1. The HyMountEcos campaign took place in June-July 2012 in the mountainous region of Karkonosze. The analysis includes remote sensing data from lidars, sun-photometers, and numerical simulations from NAAPS, MACC, DREAM8b models. Comparison of simulations with observations demonstrates the ability of models to reasonably reproduce aerosol vertical distributions and their temporal variability. However, significant differences between simulated and measured AODs were found. The best agreement was achieved for MACC model.

  2. Modelling and Observation of Mineral Dust Optical Properties over Central Europe

    Directory of Open Access Journals (Sweden)

    Chilinski Michał T.

    2016-12-01

    Full Text Available This paper is focused on Saharan dust transport to Central Europe/Poland; we compare properties of atmospheric Saharan dust using data from NAAPS, MACC, AERONET as well as observations obtained during HyMountEcos campaign in June 2012. Ten years of dust climatology shows that long-range transport of Saharan dust to Central Europe is mostly during spring and summer. HYSPLIT back-trajectories indicate airmass transport mainly in November, but it does not agree with modeled maxima of dust optical depth. NAAPS model shows maximum of dust optical depth (~0.04-0.05, 550 nm in April-May, but the MACC modeled peak is broader (~0.04. During occurrence of mineral dust over Central-Europe for 14% (NAAPS / 12% (MACC of days dust optical depths are above 0.05 and during 4% (NAAPS / 2.5% (MACC of days dust optical depths exceed 0.1. The HyMountEcos campaign took place in June-July 2012 in the mountainous region of Karkonosze. The analysis includes remote sensing data from lidars, sun-photometers, and numerical simulations from NAAPS, MACC, DREAM8b models. Comparison of simulations with observations demonstrates the ability of models to reasonably reproduce aerosol vertical distributions and their temporal variability. However, significant differences between simulated and measured AODs were found. The best agreement was achieved for MACC model.

  3. Simultaneous X-ray/optical observations of GX 9+9 (4U 1728-16)

    CERN Document Server

    Kong, A K H; Homer, L; Kuulkers, E; O'Donoghue, D

    2006-01-01

    We report on the results of the first simultaneous X-ray (RXTE) and optical (SAAO) observations of the luminous low mass X-ray binary (LMXB) GX 9+9 in 1999 August. The high-speed optical photometry revealed an orbital period of 4.1958 hr and confirmed previous observations, but with greater precision. No X-ray modulation was found at the orbital period. On shorter timescales, a possible 1.4-hr variability was found in the optical light curves which might be related to the mHz quasi-periodic oscillations seen in other LMXBs. We do not find any significant X-ray/optical correlation in the light curves. In X-rays, the colour-colour diagram and hardness-intensity diagram indicate that the source shows characteristics of an atoll source in the upper banana state, with a correlation between intensity and spectral hardness. Time-resolved X-ray spectroscopy suggests that two-component spectral models give a reasonable fit to the X-ray emission. Such models consist of a blackbody component which can be interpreted as ...

  4. Ultraviolet, Optical, and X-Ray Observations of the Type Ia Supernova 2005am with Swift

    CERN Document Server

    Brown, P J; James, C; Milne, P; Roming, P W A; Mason, K O; Page, K L; Beardmore, A P; Burrows, D; Morgan, A; Gronwall, C; Blustin, A J; Boyd, P; Still, M; Breeveld, A; De Pasquale, M; Hunsberger, S; Ivanushkina, M; Landsman, W B; McGowan, K; Poole, T; Rosen, S; Schady, P; Gehrels, N

    2005-01-01

    We present ultraviolet and optical light curves in six broadband filters and grism spectra obtained by Swift's Ultraviolet/Optical Telescope for the Type Ia supernova SN2005am. The data were collected beginning about four days before the B-band maximum, with excellent coverage of the rapid decline phase and later observations extending out to 69 days after the peak. The optical and near UV light curve match well those of SN1992A. The other UV observations constitute the first set of light curves shorter than 2500 Angstroms and allow us to compare the light curve evolution in three UV bands. The UV behavior of this and other low redshift supernovae can be used to constrain theories of progenitor evolution or to interpret optical light curves of high redshift supernovae. Using Swift's X-Ray Telescope, we also report the upper limit to SN2005am's X-ray luminosity to be 1.77 x 10^40 erg s^-1 in the 0.3--10 keV range from 58,117 s of exposure time.

  5. Optical, radio, and infrared observations of compact H II regions. V. The hourglass in M8

    Energy Technology Data Exchange (ETDEWEB)

    Woodward, C.E.; Pipher, J.L.; Helfer, H.L.; Sharpless, S.; Moneti, A.; Kozikowski, D.; Oliveri, M.; Willner, S.P.; Lacasse, M.G.; Herter, T.

    1986-04-01

    Multiwavelength observations of the inner core of the M8 Hourglass region are presented, including VLA interferometric maps, 2--4 ..mu..m and 8--13 ..mu..m spectroscopy, photometric mapping in the K (2.2 ..mu..m) and L (3.45 ..mu..m) bands and in the 3.28 ..mu..m dust-emission feature, optical CCD imaging, and optical and infrared polarimetry. The compact H II region is excited by the O7 V star Herschel 36, and its apparent bipolar structure at optical wavelengths may be due to variable line-of-sight extinction and scattered light. Standard reddening laws are not applicable in the Hourglass region. A power law extinction lambda/sup -0.78/ yields consistent agreement between ultraviolet, optical, and infrared extinction estimates and suggests that one component of the total grain distribution is on the average larger than that found in the interstellar medium. The spatial distribution of the 3.28 ..mu..m dust-emission feature shows that the feature emission is associated with the boundary layer in the H II region/molecular cloud interface. The observations favor models in which feature emission comes from small refractory grains rather than from fluorescence or thermal emission from volatile mantles.

  6. Particle Acceleration and Magnetic Field Structure in PKS 2155-304: Optical Polarimetric Observations

    CERN Document Server

    de Almeida, U Barres; Dominici, T P; Abraham, Z; Franco, G A P; Daniel, M K; Chadwick, P M; Boisson, C

    2010-01-01

    In this paper we present multiband optical polarimetric observations of the VHE blazar PKS 2155-304 made simultaneously with a H.E.S.S./Fermi high-energy campaign in 2008, when the source was found to be in a low state. The intense daily coverage of the dataset allowed us to study in detail the temporal evolution of the emission and we found that the particle acceleration timescales are decoupled from the changes in the polarimetric properties of the source. We present a model in which the optical polarimetric emission originates at the polarised mm-wave core and propose an explanation for the lack of correlation between the photometric and polarimetric fluxes. The optical emission is consistent with an inhomogeneous synchrotron source in which the large scale field is locally organised by a shock in which particle acceleration takes place. Finally, we use these optical polarimetric observations of PKS 2155-304 at a low state to propose an origin for the quiescent gamma-ray flux of the object, in an attempt t...

  7. Clear widens the field for observations of the Sun with multi-conjugate adaptive optics

    Science.gov (United States)

    Schmidt, Dirk; Gorceix, Nicolas; Goode, Philip R.; Marino, Jose; Rimmele, Thomas; Berkefeld, Thomas; Wöger, Friedrich; Zhang, Xianyu; Rigaut, François; von der Lühe, Oskar

    2017-01-01

    The multi-conjugate adaptive optics (MCAO) pathfinder Clear on the New Solar Telescope in Big Bear Lake has provided the first-ever MCAO-corrected observations of the Sun that show a clearly and visibly widened corrected field of view compared to quasi-simultaneous observations with classical adaptive optics (CAO) correction. Clear simultaneously uses three deformable mirrors, each conjugated to a different altitude, to compensate for atmospheric turbulence. While the MCAO correction was most effective over an angle that is approximately three times wider than the angle that was corrected by CAO, the full 53'' field of view did benefit from MCAO correction. We further demonstrate that ground-layer-only correction is attractive for solar observations as a complementary flavor of adaptive optics for observational programs that require homogenous seeing improvement over a wide field rather than diffraction-limited resolution. We show illustrative images of solar granulation and of a sunspot obtained on different days in July 2016, and present a brief quantitative analysis of the generalized Fried parameters of the images. The movies associated to Fig. 1 are available at http://www.aanda.org

  8. 10th Generation International Geomagnetic Reference Field

    Science.gov (United States)

    Maus, Stefan; Macmillan, Susan

    2005-04-01

    The International Association of Geomagnetism and Aeronomy (IAGA) released the 10th Generation International Geomagnetic Reference Field (IGRF) on 12 December 2004. This is the latest version of a standard mathematical description of the Earth's main magnetic field, and is used widely in studies of the Earth's deep interior, crust, ionosphere, and magnetosphere. The coefficients were finalized by a task force of IAGA, Division V, Working Group V-MOD: Geomagnetic Field Modeling. The IGRF is the product of a large collaborative effort between magnetic field modelers and the institutes around the world involved in collecting and disseminating magnetic field data from satellites and observatories. The IGRF is a series of mathematical models of the Earth's main field and its annual rate of change (secular variation). The sources of the main magnetic field are electric currents in the Earth and the magnetization of crustal rocks.

  9. Quantifying Power Grid Risk from Geomagnetic Storms

    Science.gov (United States)

    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.

  10. Improvements in geomagnetic observatory data quality

    DEFF Research Database (Denmark)

    Reda, Jan; Fouassier, Danielle; Isac, Anca

    2011-01-01

    between observatories and the establishment of observatory networks has harmonized standards and practices across the world; improving the quality of the data product available to the user. Nonetheless, operating a highquality geomagnetic observatory is non-trivial. This article gives a record...... of the current state of observatory instrumentation and methods, citing some of the general problems in the complex operation of geomagnetic observatories. It further gives an overview of recent improvements of observatory data quality based on presentation during 11th IAGA Assembly at Sopron and INTERMAGNET......Geomagnetic observatory practice and instrumentation has evolved significantly over the past 150 years. Evolution continues to be driven by advances in technology and by the need of the data user community for higher-resolution, lower noise data in near-real time. Additionally, collaboration...

  11. International Geomagnetic Reference Field: the third generation.

    Science.gov (United States)

    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

  12. Progress in Studies of Geomagnetic Navigation of Animals

    Institute of Scientific and Technical Information of China (English)

    Tian Lanxiang; Pan Yongxin; Lin Wei; Wang Yinan; Zhang Shuyi

    2005-01-01

    @@ The geomagnetic field may play a key role in orientation and navigation of many long-distance migratory animals. Taking homing and migrating birds as examples, this paper reviews recent progress in studies of geomagnetic "compass" of animals.Moreover, we propose to address two aspects in future geomagnetic orientation research: ( 1 ) what are the true components of the "map"? (2) What are the magneto-receptors and which brain areas acquire and process the geomagnetic field information ?

  13. Optical Observations of Naturally Occuring Airglow Emissions as a Tsunami Monitoring Tool

    Science.gov (United States)

    Makela, J. J.; Grawe, M.

    2016-12-01

    Over the past five years, observations of the redline emission in Earth's thermosphere, caused by the dissociative recombination of O2+, have been shown to have applications for monitoring tsunamis. This emission occurs at approximately 250-km altitude and is perturbed by tsunami-generated atmospheric gravity waves, allowing the use of optical observations made from ground-based imaging systems to study the properties of the underlying tsunami. These measurements have been shown to depend on the posture between the observation raypath and the structure of the gravity wave, making them anisotropic. New analysis methods have been shown to be effective in both determining the observability (where to look in the sky) and inferring parameters (orientation, wavelength) of these atmospheric gravity waves. Here, we present a complete review of the historical observations of tsunami-generated gravity waves made from an imaging system in Hawaii and the techniques used to analyze the data. Strengths and weaknesses of the optical observational technique as a tsunami monitoring tool will be discussed as well as possible methods and observing platforms that could be employed in the future to overcome these weaknesses.

  14. Longitudinal and geomagnetic activity modulation of the equatorial thermosphere anomaly

    Science.gov (United States)

    Lei, Jiuhou; Thayer, Jeffrey P.; Forbes, Jeffrey M.

    2010-08-01

    In this paper we examine the detailed similarities and differences between the equatorial thermosphere anomaly (ETA) and the equatorial ionization anomaly (EIA) from 20 March to 6 April 2002, when both the ETA and the EIA are distinct in the Challenging Minisatellite Payload (CHAMP) observations. The characteristics of the ETA and the EIA are obtained from the CHAMP accelerometer, in situ electron density measurements, and total electron content (TEC) above the CHAMP satellite. Our results show that the trough locations of the ETA and the EIA in latitude show a good agreement, and both correspond well with the dip magnetic equator, while the ETA crests are usually located poleward of the EIA. Meanwhile, the latitudinal locations of the ETA crests exhibit strong hemispheric asymmetry and large variability during our study interval. The longitudinal variations between the EIA and the ETA show significant differences. The EIA crests from the CHAMP observations show strong wave 4 structures, but the primary component in the ETA is wave 1. Moreover, the ETA densities show strong variations in response to geomagnetic activity, whereas CHAMP in situ electron densities and TEC at the EIA do not reflect such large day-to-day variability. Therefore, a simple EIA-ETA relationship cannot explain the dependence of the longitudinal and geomagnetic activity modulation of the ETA and the EIA. The meridional ion drag, which is significantly modulated by enhanced equatorward winds during elevated geomagnetic activity, is probably responsible for some of the observed features in the ETA, although no unambiguous explanation for ETA formation yet exists.

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

    Science.gov (United States)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2013-04-01

    From the surface of the Sun, as a result of a solar flare, are expelled a coronal mass (CME or Coronal Mass Ejection) that can be observed from the Earth through a coronagraph in white light. This ejected material can be compared to an electrically charged cloud (plasma) mainly composed of electrons, protons and other small quantities of heavier elements such as helium, oxygen and iron that run radially from the Sun along the lines of the solar magnetic field and pushing into interplanetary space. Sometimes the CME able to reach the Earth causing major disruptions of its magnetosphere: mashed in the region illuminated by the Sun and expanding in the region not illuminated. This interaction creates extensive disruption of the Earth's geomagnetic field that can be detected by a radio receiver tuned to the ELF band (Extreme Low Frequency 0-30 Hz). The Radio Emissions Project (scientific research project founded in February 2009 by Gabriele Cataldi and Daniele Cataldi), analyzing the change in the Earth's geomagnetic field through an induction magnetometer tuned between 0.001 and 5 Hz (bandwidth in which possible to observe the geomagnetic pulsations) was able to detect the existence of a close relationship between this geomagnetic perturbations and the global seismic activity M6+. During the arrival of the CME on Earth, in the Earth's geomagnetic field are generated sudden and intensive emissions that have a bandwidth including between 0 and 15 Hz, an average duration of 2-8 hours, that preceding of 0-12 hours M6+ earthquakes. Between 1 January 2012 and 31 December 2012, all M6+ earthquakes recorded on a global scale were preceded by this type of signals which, due to their characteristics, have been called "Seismic Geomagnetic Precursors" (S.G.P.). The main feature of Seismic Geomagnetic Precursors is represented by the close relationship that they have with the solar activity. In fact, because the S.G.P. are geomagnetic emissions, their temporal modulation depends

  16. Toward a possible next geomagnetic transition?

    Directory of Open Access Journals (Sweden)

    A. De Santis

    2013-09-01

    Full Text Available The geomagnetic field is subject to possible reversals or excursions of polarity during its temporal evolution. Considering that: (a the typical average time between one reversal and the next (the so-called chron is around 300 000 yr, (b the last reversal occurred around 780 000 yr ago, (c more excursions (rapid changes of polarity can occur within the same chron and (d the geomagnetic field dipole is currently decreasing, a possible imminent geomagnetic reversal or excursion would not be completely unexpected. In that case, such a phenomenon would represent one of the very few natural hazards which are really global. The South Atlantic Anomaly (SAA is a great depression of the geomagnetic field at the Earth's surface, caused by a reverse magnetic flux in the terrestrial outer core. In analogy with critical point phenomena characterised by some cumulative quantity, we fit the surface extent of this anomaly over the last 400 yr with power or logarithmic functions in reverse time, also decorated by log-periodic oscillations, whose final singularity (a critical point tc reveals a great change in the near future (2034 ± 3 yr, when the SAA area reaches almost a hemisphere. An interesting aspect that has been recently found is the possible direct connection between the SAA and the global mean sea level (GSL. That the GSL is somehow connected with SAA is also confirmed from the similar result when an analogous critical-like fit is performed over GSL: the corresponding critical point (2033 ± 11 yr agrees, within the estimated errors, with the value found for SAA. From this result, we point out the intriguing conjecture that tc would be the time of no return, after which the geomagnetic field could fall into an irreversible process of a global geomagnetic transition that could be a reversal or excursion of polarity.

  17. Toward a possible next geomagnetic critical transition?

    Science.gov (United States)

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

    2014-05-01

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

  18. Toward a possible next geomagnetic transition?

    Science.gov (United States)

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

    2013-12-01

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

  19. Stellar progenitors of black holes: insights from optical and infrared observations

    CERN Document Server

    Mirabel, I F

    2016-01-01

    Here are reviewed the insights from observations at optical and infrared wavelengths for low mass limits above which stars do not seem to end as luminous supernovae. These insights are: (1) the absence in archived images of nearby galaxies of stellar progenitors of core-collapse supernovae above 16-18 solar masses, (2) the identification of luminous-massive stars that quietly disappear without optically bright supernovae, (3) the absence in the nebular spectra of supernovae of type II-P of the nucleosynthetic products expected from progenitors above 20 solar masses, (4) the absence in color magnitude diagrams of stars in the environment of historic core-collapse supernovae of stars with >20 solar masses. From the results in these different areas of observational astrophysics, and the recently confirmed dependence of black hole formation on metallicity and redshift of progenitors, it is concluded that a large fraction of massive stellar binaries in the universe end as binary black holes.

  20. Experimental observation and investigation of the prewave zone effect in optical diffraction radiation

    Directory of Open Access Journals (Sweden)

    P. Karataev

    2008-03-01

    Full Text Available Transition radiation (TR and diffraction radiation (DR has widely been used for both electron beam diagnostics and generation of intense radiation beams in the millimeter and the submillimeter wavelength range. Recently, it was theoretically predicted that TR and DR properties change either at extremely high energies of electrons or at long radiation wavelengths. This phenomenon was called a prewave zone effect. We have performed the first observation and detailed investigation of the prewave zone effect in optical diffraction radiation at 1.28 GeV electron beam at the KEK-Accelerator Test Facility (KEK-ATF. The beam energy at KEK-ATF is definitely not the highest one achieved in the world. Since we could easily observe the effect, at higher energies it might cause serious problems. We developed and applied a method for prewave zone suppression valid for optical wavelengths. Furthermore, a method for prewave zone suppression applicable for longer radiation wavelengths is discussed.

  1. Unveiling 4U2206+54 Using Simultaneous RXTE and Optical Observations

    Science.gov (United States)

    Wilms, Joern

    We propose a 200ksec long RXTE observation of the putative Be binary 4U2206+54 to confirm the presence of a cyclotron line feature at 30keV. The confirmation of this line would allow us to determine the nature of the compact object as a neutron star, making 4U2206+54 the first cyclotron line source without X-ray pulsations. Simultaneous optical observations will furthermore allow us to shed light on the accretion process in this system, which has one of the strangest optical spectra of all Be-like systems. By studying one of the end stages of stellar evolution, this program contributes to NASA's Strategic Objectives for 2005 and Beyond: ``Explore the Universe to understand its origin, structure, evolution and destiny''.

  2. Satellite data for geomagnetic field modeling

    Science.gov (United States)

    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.

  3. Satellite Data for Geomagnetic Field Modeling

    Science.gov (United States)

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

    1992-01-01

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

  4. Bitter decoration and magneto-optical observations of vortex chains in high temperature superconductors

    Indian Academy of Sciences (India)

    T Tamegai; H Aoki; M Matsui; M Tokunaga

    2006-01-01

    In tilted magnetic fields, vortices in anisotropic superconductors form one-dimensional arrangements, called vortex chains. We have visualized vortex chains by Bitter decoration and magneto-optical technique. The fundamental energy scale for the attractive interaction between pancake and Josephson vortices is evaluated by observing vortex chains under various conditions. We also explore how the vortex chains evolve when the large in-plane field is applied or when the anisotropy parameter of the system is changed.

  5. Adaptive Optics Assisted 3D spectroscopy observations for black hole mass measurements

    OpenAIRE

    Pastorini, Guia

    2006-01-01

    The very high spatial resolution provided by Adaptive Optics assisted spectroscopic observations at 8m-class telescopes (e.g. with SINFONI at the VLT) will allow to greatly increase the number of direct black hole (BH) mass measurements which is currently very small. This is a fundamental step to investigate the tight link between galaxy evolution and BH growth, revealed by the existing scaling relations between $M_{BH}$ and galaxy structural parameters. I present preliminary results from SIN...

  6. Phase fluctuations of GPS signals and irregularities in the high latitude ionosphere during geomagnetic storm

    Science.gov (United States)

    Shagimuratov, I.; Chernouss, S.; Cherniak, Iu.; Efishov, I.; Filatov, M.; Tepenitsyna, N.

    2016-05-01

    In this report we analysed latitudinal occurrence of TEC fluctuations over Europe during October 2, 2013 geomagnetic storm. The data of GPS stations spaced in latitudinal range 68°-54° N over longitude of 20°E were involved in this investigation. The magnetograms of the IMAGE network and geomagnetic pulsations at Lovozero (68°02'N 35°00'W) and Sodankyla (67°22'N 26°38'W) observatories were used as indicator of auroral activity. During October 2, 2013 the strong geomagnetic field variations took place near 05 UT at auroral IMAGE network. We found good similarities between time development of substorm and fluctuations of GPS signals. The bay-like geomagnetic variations were followed by intensive phase fluctuations at auroral and subauroral stations. The strong short-term phase fluctuations were also found at mid-latitude Kaliningrad station near 05 UT that correspond to the maximal intense geomagnetic bay variations. This date confirms the equatorward expansion of the auroral oval. It brings in evidence also the storm time behavior of the irregularities oval obtained from multi-site GPS observations.

  7. Asteroid (4179) Toutatis size determination via optical images observed by the Chang'e-2 probe

    Science.gov (United States)

    Liu, P.; Huang, J.; Zhao, W.; Wang, X.; Meng, L.; Tang, X.

    2014-07-01

    This work is a physical and statistical study of the asteroid (4179) Toutatis using the optical images obtained by a solar panel monitor of the Chang'e-2 probe on Dec. 13, 2012 [1]. In the imaging strategy, the camera is focused at infinity. This is specially designed for the probe with its solar panels monitor's principle axis pointing to the relative velocity direction of the probe and Toutatis. The imaging strategy provides a dedicated way to resolve the size by multi-frame optical images. The inherent features of the data are: (1) almost no rotation was recorded because of the 5.41-7.35 Earth-day rotation period and the small amount of elapsed imaging time, only minutes, make the object stay in the images in a fixed position and orientation; (2) the sharpness of the upper left boundary and the vagueness of lower right boundary resulting from the direction of SAP (Sun-Asteroid-Probe angle) cause a varying accuracy in locating points at different parts of Toutatis. A common view is that direct, accurate measurements of asteroid shapes, sizes, and pole positions are now possible for larger asteroids that can be spatially resolved using the Hubble Space Telescope or large ground-based telescopes equipped with adaptive optics. For a quite complex planetary/asteroid probe study, these measurements certainly need continuous validation via a variety of ways [2]. Based on engineering parameters of the probe during the fly-by, the target spatial resolving and measuring procedures are described in the paper. Results estimated are optical perceptible size on the flyby epoch under the solar phase angles during the imaging. It is found that the perceptible size measured using the optical observations and the size derived from the radar observations by Ostro et al.~in 1995 [3], are close to one another.

  8. A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available A poleward-progressing 630 nm optical feature is observed between approximately 0100 UT and 0230 UT (0400 MLT to 0530 MLT by a meridian-scanning photometer (MSP located at Ny Ålesund, Svalbard. Simultaneous coherent HF radar measurements indicate a region of poleward-expanding backscatter with rapid sunward plasma flow velocity along the MSP meridian. Spatial maps of the backscatter indicate a stationary backscatter feature aligned obliquely with respect to the MSP meridian, which produces an impression of poleward-expansion as the MSP progresses to later MLT. Two interpretations of the observations are possible, depending on whether the arc system is considered to move (time-dependent or to be stationary in time and apparent motion is produced as the MSP meridian rotates underneath it (time-independent. The first interpretation is as a poleward motion of an east-west aligned auroral arc. In this case the appearance of the region of backscatter is not associated with the optical feature, though the velocities within it are enhanced when the two are co-located. The second interpretation is as a polar arc or theta aurora, common features of the polar cap under the prevailing IMF northwards conditions. In this case the backscatter appears as an approximately 150 km wide region adjacent to the optical arc. In both interpretations the luminosity of the optical feature appears related to the magnitude of the plasma flow velocity. The optical features presented here do not generate appreciable HF coherent backscatter, and are only identifiable in the backscatter data as a modification of the flow by the arc electrodynamics.

  9. Influence of high-latitude geomagnetic pulsations on recordings of broadband force-balanced seismic sensors

    Directory of Open Access Journals (Sweden)

    E. Kozlovskaya

    2012-08-01

    Full Text Available Seismic broadband sensors with electromagnetic feedback are sensitive to variations of surrounding magnetic field, including variations of geomagnetic field. Usually, the influence of the geomagnetic field on recordings of such seismometers is ignored. It might be justified for seismic observations at middle and low latitudes. The problem is of high importance, however, for observations in Polar Regions (above 60° geomagnetic latitude, where magnitudes of natural magnetic disturbances may be two or even three orders larger. In our study we investigate the effect of ultra-low frequency (ULF magnetic disturbances, known as geomagnetic pulsations, on the STS-2 seismic broadband sensors. The pulsations have their sources and, respectively, maximal amplitudes in the region of the auroral ovals, which surround the magnetic poles in both hemispheres at geomagnetic latitude (GMLAT between 60° and 80°. To investigate sensitivity of the STS-2 seismometer to geomagnetic pulsations, we compared the recordings of permanent seismic stations in northern Finland to the data of the magnetometers of the IMAGE network located in the same area. Our results show that temporary variations of magnetic field with periods of 40–150 s corresponding to regular Pc4 and irregular Pi2 pulsations are seen very well in recordings of the STS-2 seismometers. Therefore, these pulsations may create a serious problem for interpretation of seismic observations in the vicinity of the auroral oval. Moreover, the shape of Pi2 magnetic disturbances and their periods resemble the waveforms of glacial seismic events reported originally by Ekström (2003. The problem may be treated, however, if combined analysis of recordings of co-located seismic and magnetic instruments is used.

  10. Reversed polarity patches at the CMB and geomagnetic field reversal

    Institute of Scientific and Technical Information of China (English)

    XU; Wenyao(徐文耀); WEI; Zigang(魏自刚)

    2002-01-01

    The International Geomagnetic Reference Field models (IGRF) for 1900-2000 are used to calculate the geomagnetic field distribution in the Earth' interior from the ground surface to the core-mantle boundary (CMB) under the assumption of insulated mantle. Four reversed polarity patches, as one of the most important features of the CMB field, are revealed. Two patches with +Z polarity (downward) at the southern African and the southern American regions stand out against the background of -Z polarity (upward) in the southern hemisphere, and two patches of -Z polarity at the North Polar and the northern Pacific regions stand out against the +Z background in the northern hemisphere. During the 1900-2000 period the southern African (SAF) patch has quickly drifted westward at a speed of 0.2-0.3°/a; meanwhile its area has expanded 5 times, and the magnetic flux crossing the area has intensified 30 times. On the other hand, other three patches show little if any change during this 100-year period. Extending upward, each of the reversed polarity patches at the CMB forms a chimney-shaped "reversed polarity column" in the mantle with the bottom at the CMB. The height of the SAF column has grown rapidly from 200km in 1900 to 900km in 2000. If the column grows steadily at the same rate in the future, its top will reach to the ground surface in 600-700 years. And then a reversed polarity patch will be observed at the Earth's surface, which will be an indicator of the beginning of a magnetic field reversal. On the basis of this study, one can describe the process of a geomagnetic polarity reversal, the polarity reversal may be observed firstly in one or several local regions; then the areas of these regions expand, and at the same time, other new reversed polarity regions may appear. Thus several poles may exist during a polarity reversal.

  11. Optical outburst and mm activity of 3C 345 observed by the GASP

    Science.gov (United States)

    Larionov, V. M.; Villata, M.; Raiteri, C. M.; Carosati, D.; Ros, J. A.; Casas, R.; Bravo, O.; Melnichuk, D.; Gurwell, M. A.

    2009-10-01

    The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reports on the recent observation of a strong optical brightening of the blazar 3C 345. This is one of the 28 sources for which the GASP performs a long-term, multiwavelength monitoring. After a faint state (R ~ 17) observed in mid 2009, the brightness started to increase in July, and in August a sharp flare led to a peak of R = 16.09 +/- 0.01 on August 20; this was followed by a fast dimming and subsequent steep rebrightening up to R = 15.75 +/- 0.01 on September 20.

  12. Direct optical observation of magnetic domains in Ni-Mn-Ga martensite

    Science.gov (United States)

    Ge, Y.; Heczko, O.; Söderberg, O.; Hannula, S.-P.

    2006-08-01

    This letter reports the direct optical observation, i.e., without polarization, of the magnetic domain structure explained by a large surface relief in Ni-Mn-Ga martensite. The authors suggest that the relief is due to the different straining of the surface and the bulk caused by the internal stresses associated with the magnetic shape memory effect. As a result of the relief the projection of the (011) twin traces upon the (010) plane creates the observed zigzag pattern. The surface tilt angle calculated from the zigzag pattern is ˜3°.

  13. Optical Observation of Plasnionic Nonlocal Effects in a 2D Superlattice of Ultrasmall Gold Nanoparticles

    DEFF Research Database (Denmark)

    Shen, Hao; Chen, Li; Ferrari, Lorenzo

    2017-01-01

    in single ultrasmall silver nanopartides have been experimentally observed in single-particle spectroscopy enabled by the unprecedented high spatial resolution of electron energy loss spectroscopy (EELS). However, the unambig-optical observation of such new effects in gold nanopartides has yet not been...... reported, due to the extremely weak scattering and the obscuring fingerprint of strong interband transitions. Here we present a nanosystem, a superlattice monolayer formed by sub-10 nm gold nanopartides. Plasmon resonances are spectrally well-separated from interband transitions, while exhibiting clearly...

  14. Observation of Motion Dependent Nonlinear Dispersion with Narrow Linewidth Atoms in an Optical Cavity

    CERN Document Server

    Westergaard, Philip G; Tieri, David; Matin, Rastin; Cooper, John; Holland, Murray; Ye, Jun; Thomsen, Jan W

    2014-01-01

    As an alternative to state-of-the-art laser frequency stabilisation using ultra-stable cavities, it has been proposed to exploit the non-linear effects from coupling of atoms with a narrow atomic transition to an optical cavity. Here we have constructed such a system and observed non-linear phase shifts of a narrow optical line by strong coupling of a sample of strontium-88 atoms to an optical cavity. The sample temperature of a few mK provides a domain where the Doppler energy scale is several orders of magnitude larger than the narrow linewidth of the optical transition. This makes the system sensitive to velocity dependent multi-photon scattering events (Dopplerons) that affect the cavity transmission significantly while leaving the phase signature relatively unaffected. By varying the number of atoms and the intra-cavity power we systematically study this non-linear phase signature which displays roughly the same features as for much lower temperature samples. This demonstration in a relatively simple sys...

  15. Optical/infrared observations of the X-ray burster KS1731-260 in quiescence

    CERN Document Server

    Zurita, C; Bandyopadhyay, R M; Cackett, E M; Groot, P J; Orosz, J A; Torres, M A P; Wijnands, R

    2010-01-01

    We performed an optical/infrared study of the counterpart of the low-mass X-ray binary KS1731-260 to test its identification and obtain information about the donor. Optical and infrared images of the counterpart of KS1731-260 were taken in two different epochs (2001 and 2007) after the source returned to quiescence in X-rays. We compared those observations with obtained when KS 1731-260 was still active. We confirm the identification of KS1731-260 with the previously proposed counterpart and improve its position to RA=17:34:13.46 and DEC=-26:05:18.60. The H-band magnitude of this candidate showed a decline of ~1.7 mags from outburst to quiescence. In 2007 April we obtained R=22.8+-0.1 and I=20.9+-0.1 for KS1731-260. Similar optical brightness was measured in June 2001 and July 2007. The intrinsic optical color R-I is consistent with spectral types from F to G for the secondary although there is a large excess over that from the secondary at the infrared wavelengths. This may be due to emission from the cooler...

  16. Single-shot observation of optical rogue waves in integrable turbulence using time microscopy.

    Science.gov (United States)

    Suret, Pierre; Koussaifi, Rebecca El; Tikan, Alexey; Evain, Clément; Randoux, Stéphane; Szwaj, Christophe; Bielawski, Serge

    2016-10-07

    Optical fibres are favourable tabletop laboratories to investigate both coherent and incoherent nonlinear waves. In particular, exact solutions of the one-dimensional nonlinear Schrödinger equation such as fundamental solitons or solitons on finite background can be generated by launching periodic, specifically designed coherent waves in optical fibres. It is an open fundamental question to know whether these coherent structures can emerge from the nonlinear propagation of random waves. However the typical sub-picosecond timescale prevented-up to now-time-resolved observations of the awaited dynamics. Here, we report temporal 'snapshots' of random light using a specially designed 'time-microscope'. Ultrafast structures having peak powers much larger than the average optical power are generated from the propagation of partially coherent waves in optical fibre and are recorded with 250 femtoseconds resolution. Our experiment demonstrates the central role played by 'breather-like' structures such as the Peregrine soliton in the emergence of heavy-tailed statistics in integrable turbulence.

  17. An Optical Atmospheric Phenomenon Observed in 1670 over the City of Astrakhan Was Not a Mid-Latitude Aurora

    Science.gov (United States)

    Usoskin, I. G.; Kovaltsov, G. A.; Mishina, L. N.; Sokoloff, D. D.; Vaquero, J.

    2017-01-01

    It has recently been claimed (Zolotova and Ponyavin Solar Phys., 291, 2869, 2016; ZP16 henceforth) that a mid-latitude optical phenomenon, which took place over the city of Astrakhan in July 1670, according to Russian chronicles, were a strong aurora borealis. If this were true, it would imply a very strong or even severe geomagnetic storm during the quietest part of the Maunder minimum. However, as we argue in this article, this conclusion is erroneous and caused by a misinterpretation of the chronicle record. As a result of a thorough analysis of the chronicle text, we show that the described phenomenon occurred during the daylight period of the day ("the last morning hour"), in the south ("towards noon"), and its description does not match that of an aurora. The date of the event was also interpreted incorrectly. We conclude that this phenomenon was not a mid-latitude aurora, but an atmospheric phenomenon, the so-called sundog (or parhelion), which is a particular type of solar halo. Accordingly, the claim of a strong mid-latitude aurora during the deep Maunder Minimum is not correct and should be dismissed.

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

    Science.gov (United States)

    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.

  19. Revisiting the Jurassic Geomagnetic Reversal recorded in the Lesotho Basalt (Southern Africa)

    CERN Document Server

    Prévot, M; Thompson, J; Faynot, L; Perrin, M; Camps, P; Prevot, Michel; Roberts, Neil; Thompson, John; Faynot, Liliane; Perrin, Mireille; Camps, Pierre

    2003-01-01

    We carried out a detailed and continuous paleomagnetic sampling of the reversed to normal geomagnetic transition recorded by some 60 consecutive flow units near the base of the Lesotho Basalt (183  1 Ma). After alternating field or thermal cleaning the directions of remanence are generally well clustered within flow units. In contrast, the thermal instability of the samples did not allow to obtain reliable paleointensity determinations. The geomagnetic transition is incompletely recorded due to a gap in volcanic activity attested both by eolian deposits and a large angular distance between the field directions of the flows underlying or overlying these deposits. The transition path is noticeably different from that reported in the pioneer work of van Zijl et al. (1962). The most transitional Virtual Geomagnetic Poles are observed after the volcanic hiatus. Once continents are replaced in their relative position 180 Ma ago, the post-hiatus VGP cluster over Russia. However, two successive rebounds f...

  20. A study on precursors leading to geomagnetic storms using artificial neural network

    Science.gov (United States)

    Singh, Gaurav; Singh, A. K.

    2016-07-01

    Space weather prediction involves advance forecasting of the magnitude and onset time of major geomagnetic storms on Earth. In this paper, we discuss the development of an artificial neural network-based model to study the precursor leading to intense and moderate geomagnetic storms, following halo coronal mass ejection (CME) and related interplanetary (IP) events. IP inputs were considered within a 5-day time window after the commencement of storm. The artificial neural network (ANN) model training, testing and validation datasets were constructed based on 110 halo CMEs (both full and partial halo and their properties) observed during the ascending phase of the 24th solar cycle between 2009 and 2014. The geomagnetic storm occurrence rate from halo CMEs is estimated at a probability of 79%, by this model.

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

    Science.gov (United States)

    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.

  2. Geomagnetic effects on cosmic ray propagation under different conditions for Buenos Aires and Marambio, Argentina

    CERN Document Server

    Masías-Meza, Jimmy J

    2014-01-01

    The geomagnetic field (Bgeo) sets a lower cutoff rigidity (Rc) to the entry of cosmic particles to Earth which depends on the geomagnetic activity. From numerical simulations of the trajectory of a proton using different models for Bgeo (performed with the MAGCOS code), we use backtracking to analyze particles arriving at the location of two nodes of the net LAGO (Large Aperture Gamma ray burst Observatory) that will be built in the near future: Buenos Aires and Marambio (Antarctica), Argentina. We determine the asymptotic trajectories and the values of Rc for different incidence directions, for each node. Simulations were done using several models for Bgeo that emulate different geomagnetic conditions. The presented results will help to make analysis of future observations of the flux of cosmic rays done at these two LAGO nodes.

  3. PAMELA's measurements of geomagnetic cutoff variations during solar energetic particle events

    CERN Document Server

    Bruno, A; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bravar, U; Cafagna, F; Campana, D; Carbone, R; Carlson, P; Casolino, M; Castellini, G; Christian, E C; De Donato, C; de Nolfo, G A; De Santis, C; De Simone, N; Di Felice, V; Formato, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S; Krutkov, S Y; Kvashnin, A N; Lee, M; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergè, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Palma, F; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Ryan, J M; Sarkar, R; Scotti, V; Simon, M; Sparvoli, R; Spillantini, P; Stochaj, S; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Zverev, V G

    2015-01-01

    Data from the PAMELA satellite experiment were used to measure the geomagnetic cutoff for high-energy ($\\gtrsim$ 80 MeV) protons during the solar particle events on 2006 December 13 and 14. The variations of the cutoff latitude as a function of rigidity were studied on relatively short timescales, corresponding to single spacecraft orbits (about 94 minutes). Estimated cutoff values were cross-checked with those obtained by means of a trajectory tracing approach based on dynamical empirical modeling of the Earth's magnetosphere. We find significant variations in the cutoff latitude, with a maximum suppression of about 6 deg for $\\sim$80 MeV protons during the main phase of the storm. The observed reduction in the geomagnetic shielding and its temporal evolution were compared with the changes in the magnetosphere configuration, investigating the role of IMF, solar wind and geomagnetic (Kp, Dst and Sym-H indexes) variables and their correlation with PAMELA cutoff results.

  4. ESO Imaging Survey. Hubble Deep Field South Optical-Infrared Observations, Data Reduction and Photometry

    CERN Document Server

    Da Costa, L N; Rengelink, R B; Zaggia, S R; Benoist, C; Erben, T; Wicenec, A; Scodeggio, M; Olsen, L F; Guarnieri, M D; Deul, E; D'Odorico, S; Hook, R N; Moorwood, A F M; Slijkhuis, R

    1998-01-01

    This paper presents ground-based data obtained from deep optical and infrared observations of the HST Hubble Deep Field South (HDF-S) field carried out at the ESO 3.5 New Technology Telescope (NTT). These data were taken as part of the ESO Imaging Survey (EIS) program, a public survey coordinated by ESO and member states, in preparation for the first year of operation of the VLT. Deep CCD images are available for five optical passbands, reaching 2 sigma limiting magnitudes of U_AB~27.0, B_AB~26.5, V_AB~26, R_AB~26, I_AB~25, covering a region of ~25 square arcmin, which includes the HST WPFC2 field. The infrared observations cover a total area of ~42 square arcmin and include both the HST WFPC2 and STIS fields. The observations of the WFPC2 region were conducted in JHKs passbands, reaching J_AB~25, and H_AB and K_AB~24.0. Due to time constraints, the adjacent field, covering the STIS field, has been observed only in R, I and JHKs, while no observations were conducted covering the NIC3 field. This paper describ...

  5. Magnetic signatures of ionospheric and magnetospheric current systems during geomagnetic quiet conditions - An overview

    DEFF Research Database (Denmark)

    Olsen, Nils; Stolle, Claudia

    2016-01-01

    High-precision magnetic measurements taken by LEO satellites (flying at altitudes between 300 and 800 km) allow for studying the ionosphericand 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 observationsin space, such as provided by the Swarm satellite constellation mission, inorder 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 signatureswith Swarm satellite observations....

  6. An Advanced System for Monitoring Geomagnetic Environments by the Japan Meteorological Agency

    Directory of Open Access Journals (Sweden)

    Yasuhiro Yasuhiro

    2011-06-01

    Full Text Available The Japan Meteorological Agency (JMA has developed an advanced system to monitor geomagnetic environments consisting of magnetometers and monitoring cameras. The new system calculates the magnetic moments and positions of sources of artificial disturbances and then visually identifies the sources. The intensity and location of a source of artificial disturbance are calculated assuming the source is a magnetic dipole. This new system was installed at two branch observatories operated by the JMA, which will enable the remote monitoring of sites for geomagnetic observations from the headquarters at Kakioka Magnetic Observatory.

  7. Plasmaspheric dynamics resulting from the hallowe'en 2003 geomagnetic storms

    OpenAIRE

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

    2009-01-01

    Cross-phase-derived plasma mass density trends during the Hallowe'en 2003 geomagnetic storms are presented for 38° magnetic latitude 63° (1.61 ≤ L ≤ 5.10), using data from the SAMNET (Subauroral Magnetometer Network), BGS (British Geological Survey), and SEGMA (South European Geomagnetic Array), ground-based magnetometer arrays in Europe. At all latitudes monitored, a rapid increase of total mass density is observed immediately following the initial storm sudden commencement at 0611 UT on 29 ...

  8. Confronting simulations of optically thick gas in massive halos with observations at z = 2-3

    Energy Technology Data Exchange (ETDEWEB)

    Fumagalli, Michele [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Hennawi, Joseph F. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Prochaska, J. Xavier [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Kasen, Daniel [Department of Physics, University of California, 366 LeConte, Berkeley, CA 94720 (United States); Dekel, Avishai [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Ceverino, Daniel [Departamento de Física Téorica, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Primack, Joel, E-mail: mfumagalli@obs.carnegiescience.edu [Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2014-01-01

    Cosmological hydrodynamic simulations predict the physical state of baryons in the circumgalactic medium (CGM), which can be directly tested via quasar absorption line observations. We use high-resolution 'zoom-in' simulations of 21 galaxies to characterize the distribution of neutral hydrogen around halos in the mass range M {sub vir} ∼ 2 × 10{sup 11} to 4 × 10{sup 12} M {sub ☉} at z ∼ 2. We find that both the mass fraction of cool (T ≤ 3 × 10{sup 4} K) gas and the covering fraction of optically thick Lyman limit systems (LLSs) depend only weakly on halo mass, even around the critical value for the formation of stable virial shocks. The covering fraction of LLSs interior to the virial radius varies between f {sub c} ∼ 0.05-0.2, with significant scatter among halos. Our simulations of massive halos (M {sub vir} ≥ 10{sup 12} M {sub ☉}) underpredict the covering fraction of optically thick gas observed in the quasar CGM by a large factor. The reason for this discrepancy is unclear, but several possibilities are discussed. In the lower mass halos (M {sub vir} ≥ 5 × 10{sup 11} M {sub ☉}) hosting star-forming galaxies, the predicted covering factor agrees with observations; however, current samples of quasar-galaxy pairs are too small for a conclusive comparison. To overcome this limitation, we propose a new observable: the small-scale autocorrelation function of optically thick absorbers detected in the foreground of close quasar pairs. We show that this new observable can constrain the underlying dark halos hosting LLSs at z ∼ 2-3, as well as the characteristic size and covering factor of the CGM.

  9. Kristian Birkeland's pioneering investigations of geomagnetic disturbances

    Science.gov (United States)

    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

  10. What causes geomagnetic activity during sunspot minimum

    CERN Document Server

    Kirov, Boian; Georgieva, Katya; Obridko, Vladimir

    2014-01-01

    The average geomagnetic activity during sunspot minimum has been continuously decreasing in the last four cycles. The geomagnetic activity is caused by both interplanetary disturbances - coronal mass ejections and high speed solar wind streams, and the background solar wind over which these disturbances ride. We show that the geomagnetic activity in cycle minimum does not depend on the number and parameters of coronal mass ejections or high speed solar wind streams, but on the background solar wind. The background solar wind has two components: slower and faster. The source of the slower component is the heliospheric current sheet, and of the faster one the polar coronal holes. It is supposed that the geomagnetic activity in cycle minimum is determined by the thickness of the heliospheric current sheet which is related to the portions of time the Earth spends in slow and in fast solar wind. We demonstrate that it is also determined by the parameters of these two components of the background solar wind which v...

  11. Geomagnetic referencing in the arctic environment

    Science.gov (United States)

    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.

  12. Search for neutrinos from transient sources with the ANTARES telescope and optical follow-up observations

    Science.gov (United States)

    Ageron, Michel; Al Samarai, Imen; Akerlof, Carl; Basa, Stéphane; Bertin, Vincent; Boer, Michel; Brunner, Juergen; Busto, Jose; Dornic, Damien; Klotz, Alain; Schussler, Fabian; Vallage, Bertrand; Vecchi, Manuela; Zheng, Weikang

    2012-11-01

    The ANTARES telescope is well suited to detect neutrinos produced in astrophysical transient sources as it can observe a full hemisphere of the sky at all the times with a duty cycle close to unity and an angular resolution better than 0.5°. Potential sources include gamma-ray bursts (GRBs), core collapse supernovae (SNe), and flaring active galactic nuclei (AGNs). To enhance the sensitivity of ANTARES to such sources, a new detection method based on coincident observations of neutrinos and optical signals has been developed. A fast online muon track reconstruction is used to trigger a network of small automatic optical telescopes. Such alerts are generated one or two times per month for special events such as two or more neutrinos coincident in time and direction or single neutrinos of very high energy. Since February 2009, ANTARES has sent 37 alert triggers to the TAROT and ROTSE telescope networks, 27 of them have been followed. First results on the optical images analysis to search for GRBs are presented.

  13. Search for neutrinos from transient sources with the ANTARES telescope and optical follow-up observations

    Energy Technology Data Exchange (ETDEWEB)

    Ageron, Michel [CPPM, CNRS/IN2P3 - Universite de Mediterranee, 163 avenue de Luminy, 13288 Marseille Cedex 09 (France); Al Samarai, Imen, E-mail: samarai@cppm.in2p3.fr [CPPM, CNRS/IN2P3 - Universite de Mediterranee, 163 avenue de Luminy, 13288 Marseille Cedex 09 (France); Akerlof, Carl [Randall Laboratory of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109-1040 (United States); Basa, Stephane [LAM, BP8, Traverse du siphon, 13376 Marseille Cedex 12 (France); Bertin, Vincent [CPPM, CNRS/IN2P3 - Universite de Mediterranee, 163 avenue de Luminy, 13288 Marseille Cedex 09 (France); Boer, Michel [OHP, 04870 Saint Michel de l' Observatoire (France); Brunner, Juergen; Busto, Jose; Dornic, Damien [CPPM, CNRS/IN2P3 - Universite de Mediterranee, 163 avenue de Luminy, 13288 Marseille Cedex 09 (France); Klotz, Alain [OHP, 04870 Saint Michel de l' Observatoire (France); IRAP, 9 avenue du colonel Roche, 31028 Toulouse Cedex 4 (France); Schussler, Fabian; Vallage, Bertrand [CEA-IRFU, centre de Saclay, 91191 Gif-sur-Yvette (France); Vecchi, Manuela [CPPM, CNRS/IN2P3 - Universite de Mediterranee, 163 avenue de Luminy, 13288 Marseille Cedex 09 (France); Zheng, Weikang [Randall Laboratory of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109-1040 (United States)

    2012-11-11

    The ANTARES telescope is well suited to detect neutrinos produced in astrophysical transient sources as it can observe a full hemisphere of the sky at all the times with a duty cycle close to unity and an angular resolution better than 0.5 Degree-Sign . Potential sources include gamma-ray bursts (GRBs), core collapse supernovae (SNe), and flaring active galactic nuclei (AGNs). To enhance the sensitivity of ANTARES to such sources, a new detection method based on coincident observations of neutrinos and optical signals has been developed. A fast online muon track reconstruction is used to trigger a network of small automatic optical telescopes. Such alerts are generated one or two times per month for special events such as two or more neutrinos coincident in time and direction or single neutrinos of very high energy. Since February 2009, ANTARES has sent 37 alert triggers to the TAROT and ROTSE telescope networks, 27 of them have been followed. First results on the optical images analysis to search for GRBs are presented.

  14. Direct observation of exceptional points in coupled photonic-crystal lasers with asymmetric optical gains

    Science.gov (United States)

    Kim, Kyoung-Ho; Hwang, Min-Soo; Kim, Ha-Reem; Choi, Jae-Hyuck; No, You-Shin; Park, Hong-Gyu

    2016-12-01

    Although counter-intuitive features have been observed in non-Hermitian optical systems based on micrometre-sized cavities, the achievement of a simplified but unambiguous approach to enable the efficient access of exceptional points (EPs) and the phase transition to desired lasing modes remains a challenge, particularly in wavelength-scale coupled cavities. Here, we demonstrate coupled photonic-crystal (PhC) nanolasers with asymmetric optical gains, and observe the phase transition of lasing modes at EPs through tuning of the area of graphene cover on one PhC cavity and systematic scanning photoluminescence measurements. As the gain contrast between the two identical PhC cavities exceeds the intercavity coupling, the phase transition occurs from the bonding/anti-bonding lasing modes to the single-amplifying lasing mode, which is confirmed by the experimental measurement of the mode images and the theoretical modelling of coupled cavities with asymmetric gains. In addition, we demonstrate active tuning of EPs by controlling the optical loss of graphene through electrical gating.

  15. VLBI observations of a flared optical quasar CGRaBS J0809+5341

    CERN Document Server

    An, Tao; Paragi, Zsolt; Frey, Sandor; Gurvits, Leonid I; Gabanyi, Krisztina E

    2016-01-01

    A bright optical flare was detected in the high-redshift ($z=2.133$) quasar CGRaBS J0809+5341 on 2014 April 13. The absolute magnitude of the object reached $-30.0$ during the flare, making it the brightest one (in flaring stage) among all known quasars so far. The 15 GHz flux density of CGRaBS J0809+5341 monitored in the period from 2008 to 2016 also reached its peak at the same time. To reveal any structural change possibly associated with the flare in the innermost radio structure of the quasar, we conducted a pilot very long baseline interferometry (VLBI) observation of CGRaBS J0809+5341 using the European VLBI Network (EVN) at 5 GHz on 2014 November 18, about seven months after the prominent optical flare. Three epochs of follow-up KaVA (Korean VLBI Network and VLBI Exploration of Radio Astrometry Array) observations were carried out at 22 and 43 GHz frequencies from 2015 February 25 to June 4, with the intention of exploring a possibly emerging new radio jet component associated with the optical flare. ...

  16. Optimal design of an earth observation optical system with dual spectral and high resolution

    Science.gov (United States)

    Yan, Pei-pei; Jiang, Kai; Liu, Kai; Duan, Jing; Shan, Qiusha

    2017-02-01

    With the increasing demand of the high-resolution remote sensing images by military and civilians, Countries around the world are optimistic about the prospect of higher resolution remote sensing images. Moreover, design a visible/infrared integrative optic system has important value in earth observation. Because visible system can't identify camouflage and recon at night, so we should associate visible camera with infrared camera. An earth observation optical system with dual spectral and high resolution is designed. The paper mainly researches on the integrative design of visible and infrared optic system, which makes the system lighter and smaller, and achieves one satellite with two uses. The working waveband of the system covers visible, middle infrared (3-5um). Dual waveband clear imaging is achieved with dispersive RC system. The focal length of visible system is 3056mm, F/# is 10.91. And the focal length of middle infrared system is 1120mm, F/# is 4. In order to suppress the middle infrared thermal radiation and stray light, the second imaging system is achieved and the narcissus phenomenon is analyzed. The system characteristic is that the structure is simple. And the especial requirements of the Modulation Transfer Function (MTF), spot, energy concentration, and distortion etc. are all satisfied.

  17. Optical Observation of Plasmonic Nonlocal Effects in a 2D Superlattice of Ultrasmall Gold Nanoparticles.

    Science.gov (United States)

    Shen, Hao; Chen, Li; Ferrari, Lorenzo; Lin, Meng-Hsien; Mortensen, N Asger; Gwo, Shangjr; Liu, Zhaowei

    2017-03-02

    The advances in recent nanofabrication techniques have facilitated explorations of metal structures into nanometer scales, where the traditional local-response Drude model with hard-wall boundary conditions fails to accurately describe their optical responses. The emerging nonlocal effects in single ultrasmall silver nanoparticles have been experimentally observed in single-particle spectroscopy enabled by the unprecedented high spatial resolution of electron energy loss spectroscopy (EELS). However, the unambiguous optical observation of such new effects in gold nanoparticles has yet not been reported, due to the extremely weak scattering and the obscuring fingerprint of strong interband transitions. Here we present a nanosystem, a superlattice monolayer formed by sub-10 nm gold nanoparticles. Plasmon resonances are spectrally well-separated from interband transitions, while exhibiting clearly distinguishable blueshifts compared to predictions by the classical local-response model. Our far-field spectroscopy was performed by a standard optical transmission and reflection setup, and the results agreed excellently with the hydrodynamic nonlocal model, opening a simple and widely accessible way for addressing quantum effects in nanoplasmonic systems.

  18. Optical properties of Titan's aerosols: comparison between DISR/Huygens observations and VIMS/Cassini solar occultation observations

    Science.gov (United States)

    Marmuse, Florian; Sotin, Christophe; Lawrence, Kenneth J.; Brown, Robert H.; Baines, Kevin; Buratti, Bonnie; Clark, Roger Nelson; Nicholson, Philip D.

    2016-10-01

    Titan, the only satellite with a dense atmosphere, presents a hydrocarbon cycle that includes the formation and sedimentation of organic aerosols. The optical properties of Titan's haze inferred from measurement of the Huygens probe were recently revisited by Doose et al. (Icarus, 2016). The present study uses the solar occultation observations in equatorial regions of Titan that have been acquired by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft to infer similar information in a broader wavelength range. Preliminary studies have proven the interest of those solar occultation data in the seven atmospheric windows to constrain the aerosol number density, but could not directly compare with the Descent Imager and Spectral Radiometer (DISR) data because models predict that the density profile vary with latitude. The present study compares the DISR measurements of aerosol extinction coefficients and the solar occultation data acquired by the VIMS instrument onboard Cassini. These sets of data differ in their acquisition method and time, spectral range, and altitude: the DISR measurements have been taken in 2005, along a vertical line of sight, in the visible spectral range (490-950nm) and under 140km of altitude. The relevant solar occultation data at equator have been acquired in 2009, along a horizontal line of sight, in the IR range (0.9-5.1µm), with sun light scanning all altitudes for a long enough wavelength, namely in the five-micron atmospheric window. These sets of data have been analyzed previously, separately and using different models. Here, we present a cross analysis of these sets of data, that allows us to test the different models describing the density profile of aerosols. In addition to providing wavelength dependence of the extinction coefficient, the comparison allows us to assess the impact of refraction in Titan's atmosphere. It also provides optical depth and scattering properties that are crucial information

  19. OPTICAL PHOTOMETRIC GTC/OSIRIS OBSERVATIONS OF THE YOUNG MASSIVE ASSOCIATION CYGNUS OB2

    Energy Technology Data Exchange (ETDEWEB)

    Guarcello, M. G.; Wright, N. J.; Drake, J. J.; Aldcroft, T.; Kashyap, V. L. [Smithsonian Astrophysical Observatory, MS-67, 60 Garden Street, Cambridge, MA 02138 (United States); Garcia-Alvarez, D. [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain); Drew, J. E. [CAR/STRI, University of Hertfordshire, College Lane, Hatfield, AL10 9AB (United Kingdom)

    2012-10-15

    In order to fully understand the gravitational collapse of molecular clouds, the star formation process, and the evolution of circumstellar disks, these phenomena must be studied in different Galactic environments with a range of stellar contents and positions in the Galaxy. The young massive association Cygnus OB2, in the Cygnus-X region, is a unique target to study how star formation and the evolution of circumstellar disks proceed in the presence of a large number of massive stars. We present a catalog obtained with recent optical observations in the r, i, z filters with OSIRIS, mounted on the 10.4 m Gran Telescopio CANARIAS telescope, which is the deepest optical catalog of Cyg OB2 to date. The catalog consists of 64,157 sources down to M = 0.15 M{sub Sun} at the adopted distance and age of Cyg OB2. A total of 38,300 sources have good photometry in all three bands. We combined the optical catalog with existing X-ray data of this region, in order to define the cluster locus in the optical diagrams. The cluster locus in the r - i versus i - z diagram is compatible with an extinction of the optically selected cluster members in the 2.64{sup m} < A{sub V} < 5.57{sup m} range. We derive an extinction map of the region, finding a median value of A{sub V} = 4.33{sup m} in the center of the association, decreasing toward the northwest. In the color-magnitude diagrams, the shape of the distribution of main-sequence stars is compatible with the presence of an obscuring cloud in the foreground {approx}850 {+-} 25 pc from the Sun.

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

    Science.gov (United States)

    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.

  1. Observation of vacuum-enhanced electron spin resonance of optically levitated nanodiamonds

    Science.gov (United States)

    Li, Tongcang; Hoang, Thai; Ahn, Jonghoon; Bang, Jaehoon

    Electron spins of diamond nitrogen-vacancy (NV) centers are important quantum resources for nanoscale sensing and quantum information. Combining such NV spin systems with levitated optomechanical resonators will provide a hybrid quantum system for many novel applications. Here we optically levitate a nanodiamond and demonstrate electron spin control of its built-in NV centers in low vacuum. We observe that the strength of electron spin resonance (ESR) is enhanced when the air pressure is reduced. To better understand this novel system, we also investigate the effects of trap power and measure the absolute internal temperature of levitated nanodiamonds with ESR after calibration of the strain effect. Our results show that optical levitation of nanodiamonds in vacuum not only can improve the mechanical quality of its oscillation, but also enhance the ESR contrast, which pave the way towards a novel levitated spin-optomechanical system for studying macroscopic quantum mechanics. The results also indicate potential applications of NV centers in gas sensing.

  2. Constraints on Disks Models of The Big Blue Bump from UV/Optical/IR Observations

    CERN Document Server

    Antonucci, R

    1998-01-01

    Optical/UV observations provide many constraints on accretion disk models of AGN which aren't always appreciated by modelers of the X-ray emission (or sometimes even of the optical/UV emission). The spectral behavior at the Ly edge, the polarization, the continuum slopes and breaks, and the variability timescales and phasing all conflict with simple models and strongly constrain the more Baroque ones. Partial-covering absorbers and microlensing data suggest that the radiation is not released simply according to where the potential drop (modified by standard viscous transport) takes place. On the other hand, the orientation-based unified model is in accord with the K-\\alpha inclination distributions for the AGN spectral classes, basing the latter on the limited existing data and theoretical understanding.

  3. Coherent optical transients observed in rubidium atomic line filtered Doppler velocimetry experiments

    Energy Technology Data Exchange (ETDEWEB)

    Fajardo, Mario E., E-mail: mario.fajardo@eglin.af.mil; Molek, Christopher D.; Vesely, Annamaria L. [Air Force Research Laboratory, Munitions Directorate, Ordnance Division, Energetic Materials Branch, AFRL/RWME, 2306 Perimeter Road, Eglin AFB, Florida 32542-5910 (United States)

    2015-10-14

    We report the first successful results from our novel Rubidium Atomic Line Filtered (RALF) Doppler velocimetry apparatus, along with unanticipated oscillatory signals due to coherent optical transients generated within pure Rb vapor cells. RALF is a high-velocity and high-acceleration extension of the well-known Doppler Global Velocimetry (DGV) technique for constructing multi-dimensional flow velocity vector maps in aerodynamics experiments [H. Komine, U.S. Patent No. 4,919,536 (24 April 1990)]. RALF exploits the frequency dependence of pressure-broadened Rb atom optical absorptions in a heated Rb/N{sub 2} gas cell to encode the Doppler shift of reflected near-resonant (λ{sub 0} ≈ 780.24 nm) laser light onto the intensity transmitted by the cell. The present RALF apparatus combines fiber optic and free-space components and was built to determine suitable operating conditions and performance parameters for the Rb/N{sub 2} gas cells. It yields single-spot velocities of thin laser-driven-flyer test surfaces and incorporates a simultaneous Photonic Doppler Velocimetry (PDV) channel [Strand et al., Rev. Sci. Instrum. 77, 083108 (2006)] for validation of the RALF results, which we demonstrate here over the v = 0 to 1 km/s range. Both RALF and DGV presume the vapor cells to be simple Beer's Law optical absorbers, so we were quite surprised to observe oscillatory signals in experiments employing low pressure pure Rb vapor cells. We interpret these oscillations as interference between the Doppler shifted reflected light and the Free Induction Decay (FID) coherent optical transient produced within the pure Rb cells at the original laser frequency; this is confirmed by direct comparison of the PDV and FID signals. We attribute the different behaviors of the Rb/N{sub 2} vs. Rb gas cells to efficient dephasing of the atomic/optical coherences by Rb-N{sub 2} collisions. The minimum necessary N{sub 2} buffer gas density ≈0.3 amagat translates into a

  4. Solar cycle distribution of major geomagnetic storms

    Institute of Scientific and Technical Information of China (English)

    Gui-Ming Le; Zi-Yu Cai; Hua-Ning Wang; Zhi-Qiang Yin; Peng Li

    2013-01-01

    We examine the solar cycle distribution of major geomagnetic storms (Dst ≤-100 nT),including intense storms at the level of-200 nT< Dst ≤-100 nT,great storms at-300 nT< Dst ≤-200 nT,and super storms at Dst ≤-300 nT,which occurred during the period of 1957-2006,based on Dst indices and smoothed monthly sunspot numbers.Statistics show that the majority (82%) of the geomagnetic storms at the level of Dst ≤-100 nT that occurred in the study period were intense geomagnetic storms,with 12.4% ranked as great storms and 5.6% as super storms.It is interesting to note that about 27% of the geomagnetic storms that occurred at all three intensity levels appeared in the ascending phase of a solar cycle,and about 73% in the descending one.Statistics also show that 76.9% of the intense storms,79.6% of the great storms and 90.9% of the super storms occurred during the two years before a solar cycle reached its peak,or in the three years after it.The correlation between the size of a solar cycle and the percentage of major storms that occurred,during the period from two years prior to maximum to three years after it,is investigated.Finally,the properties of the multi-peak distribution for major geomagnetic storms in each solar cycle is investigated.

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

    Science.gov (United States)

    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.

  6. Multiple Observing Modes for Wide-field Optical Surveillance of GEO Space

    Science.gov (United States)

    McGraw, J.; Zimmer, P.; Ackermann, M.

    2016-09-01

    Very wide field of view optical sensors with silicon detectors are being used in multiple survey modes by J. T. McGraw and Associates to provide persistent, affordable surveillance of GEO space to faint limiting magnitudes. Examples include: classical staring mode with typical integration times of seconds provided by multiple co-directed sensors to provide a deep mosaic of tens of square degrees per exposure to faint limiting magnitude b) step-and-stare observations of several second integration time from which a continuous, overlapped, mosaicked image of GEO space can be provided time-delay and integrate (TDI) imagery obtained by driving the telescope in declination and stepping the telescope in the E-W direction, which produces repeated, overlapping (if desired), synoptic images of GEO space. With current 350 mm diameter optics, detection limits for concentrated observations (e.g. "neighborhood watch") detection limits of magnitude 18 are achieved, and for uncued survey the detection limits are fainter than magnitude 16. Each of these techniques can employ multiple telescopes to obtain search rates in excess of 1000 square degrees per hour, allowing complete uncued CONUS GEO surveillance to +/- 15 degrees latitude every two nighttime hours. With appropriate placement, sensors could provide complete coverage of GEO to these limiting magnitudes at the same survey rate. At each step of the development of this unique capability we discuss the fundamental underlying physical principals of optics, detectors, search modes and siting that enable this survey, a valuable adjunct to RF, radar, GEODSS and other optical surveys of GEO space.

  7. Observation and measurement of "giant" dispersive optical non-linearities in an ensemble of cold Rydberg atoms

    CERN Document Server

    Parigi, Valentina; Stanojevic, Jovica; Hilliard, Andrew J; Nogrette, Florence; Tualle-Brouri, Rosa; Ourjoumtsev, Alexei; Grangier, Philippe

    2012-01-01

    We observe and measure dispersive optical non-linearities in an ensemble of cold Rydberg atoms placed inside an optical cavity. The experimental results are in agreement with a simple model where the optical non-linearities are due to the progressive appearance of a Rydberg blockaded volume within the medium. The measurements allow a direct estimation of the "blockaded fraction" of atoms within the atomic ensemble.

  8. Accretion onto Supermassive Black Holes in Quasars: Learning from Optical/UV Observations

    CERN Document Server

    Marziani, P; Sulentic, J W; Marziani, Paola; Dultzin-Hacyan, Deborah; Sulentic, Jack W.

    2006-01-01

    Accretion processes in quasars and active galactic nuclei are still poorly understood, especially as far as the connection between observed spectral properties and physical parameters is concerned. Quasars show an additional degree of complexity compared to stars that is related to anisotropic emission/obscuration influencing the observed properties in most spectral ranges. This complicating factor has hampered efforts to define the equivalent of an Hertzsprung-Russel diagram for quasars. Even if it has recently become possible to estimate black hole mass and Eddington ratio for sources using optical and UV broad emission lines, the results are still plagued by large uncertainties. Nevertheless, robust trends are emerging from multivariate analysis of large spectral datasets of quasars. A firm observational basis is being laid out by accurate measurements of broad emission line properties especially when the source rest-frame is known. We consider the most widely discussed correlations (i.e. the so-called "ei...

  9. Subaru Telescope adaptive optics observations of gravitationally lensed quasars in the Sloan Digital Sky Survey

    CERN Document Server

    Rusu, Cristian E; Minowa, Yosuke; Iye, Masanori; Inada, Naohisa; Oya, Shin; Kayo, Issha; Hayano, Yutaka; Hattori, Masayuki; Saito, Yoshihiko; Ito, Meguru; Pyo, Tae-Soo; Terada, Hiroshi; Takami, Hideki; Watanabe, Makoto

    2015-01-01

    We present the results of an imaging observation campaign conducted with the Subaru Telescope adaptive optics system (IRCS+AO188) on 26 gravitationally lensed quasars (24 doubles, 1 quad, and 1 possible triple) from the SDSS Quasar Lens Search. We develop a novel modelling technique that fits analytical and hybrid point spread functions (PSFs), while simultaneously measuring the relative astrometry, photometry, as well as the lens galaxy morphology. We account for systematics by simulating the observed systems using separately observed PSF stars. The measured relative astrometry is comparable with that typically achieved with the Hubble Space Telescope, even after marginalizing over the PSF uncertainty. We model for the first time the quasar host galaxies in 5 systems, without a-priory knowledge of the PSF, and show that their luminosities follow the known correlation with the mass of the supermassive black hole. For each system, we obtain mass models far more accurate than those previously published from low...

  10. X-RAY AND OPTICAL OBSERVATIONS OF A 0535+26

    Energy Technology Data Exchange (ETDEWEB)

    Camero-Arranz, A.; Finger, M. H. [Universities Space Research Association, Huntsville, AL 35806 (United States); Wilson-Hodge, C. A.; Jenke, P. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Steele, I. [Liverpool J. Moore' s University, Kingsway House, Hatton Garden, Liverpool L3 2AJ (United Kingdom); Coe, M. J.; McBride, V. A. [University of Southampton, University Road, Southampton SO17 1BJ (United Kingdom); Gutierrez-Soto, J. [Instituto de Astrofisica de Andalucia, Glorieta de la Astronomia, s/n, E-18008, Granada (Spain); Kretschmar, P. [ESA/ESAC, Madrid (Spain); Caballero, I.; Rodriguez, J. [AIM-CEA Saclay, Paris (France); Yan, J. [Purple Mountain Observatory, Chinese Academy of Sciences, Beijing (China); Suso, J. [University of Valencia, Poligono de la Coma, s/n, 46980 Paterna (Spain); Case, G.; Cherry, M. L. [Louisiana State University, Boton Rouge, LA 70803 (United States); Guiriec, S. [NASA GSFC, Greenbelt, MD 20771 (United States)

    2012-07-20

    We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A 0535+26 with the Fermi/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the context of the rich historical data (since {approx}1978) and discussed in terms of the neutron-star-Be-disk interaction. The Be circumstellar disk was exceptionally large just before the 2009 December giant outburst, which may explain the origin of the unusual recent X-ray activity of this source. We found a peculiar evolution of the pulse profile during this giant outburst, with the two main components evolving in opposite ways with energy. A hard 30-70 mHz X-ray quasi-periodic oscillation was detected with GBM during this 2009 December giant outburst. It becomes stronger with increasing energy and disappears at energies below 25 keV. In the long term a strong optical/X-ray correlation was found for this system, however in the medium term the H{alpha} equivalent width and the V-band brightness showed an anti-correlation after {approx}2002 August. Each giant X-ray outburst occurred during a decline phase of the optical brightness, while the H{alpha} showed a strong emission. In late 2010 and before the 2011 February outburst, rapid V/R variations are observed in the strength of the two peaks of the H{alpha} line. These had a period of {approx}25 days and we suggest the presence of a global one-armed oscillation to explain this scenario. A general pattern might be inferred, where the disk becomes weaker and shows V/R variability beginning {approx}6 months following a giant outburst.

  11. Optical and Ultraviolet Observations of the Very Young Type IIP SN 2014cx in NGC 337

    CERN Document Server

    Huang, Fang; Zampieri, Luca; Pumo, Maria Letizia; Arcavi, Iair; Brown, Peter J; Graham, Melissa L; Filippenko, Alexei V; Zheng, WeiKang; Hosseinzadeh, Griffin; Howell, D Andrew; McCully, Curtis; Rui, Liming; Valenti, Stefano; Zhang, Tianmeng; Zhang, Jujia; Zhang, Kaicheng; Wang, Lifan

    2016-01-01

    Extensive photometric and spectroscopic observations are presented for SN 2014cx, a type IIP supernova (SN) exploding in the nearby galaxy NGC 337. The observations are performed in optical and ultraviolet bands, covering from -20 to +400 days from the peak light. The stringent detection limit from prediscovery images suggests that this supernova was actually detected within about 1 day after explosion. Evolution of the very early-time light curve of SN 2014cx is similar to that predicted from a shock breakout and post-shock cooling decline before reaching the optical peak. Our photometric observations show that SN 2014cx has a plateau duration of ~ 100 days, an absolute V-band magnitude of ~ -16.5 mag at t~50 days, and a nickel mass of 0.056+-0.008 Msun. The spectral evolution of SN 2014cx resembles that of normal SNe IIP like SN 1999em and SN 2004et, except that it has a slightly higher expansion velocity (~ 4200 km/s at 50 days). From the cooling curve of photospheric temperature, we derive that the progen...

  12. Chemotaxis study using optical tweezers to observe the strength and directionality of forces of Leishmania amazonensis

    Science.gov (United States)

    Pozzo, Liliana d. Y.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Ayres, Diana C.; Giorgio, Selma; Cesar, Carlos L.

    2006-08-01

    The displacements of a dielectric microspheres trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences. This system can measure forces on the 50 femto Newtons to 200 pico Newtons range, of the same order of magnitude of a typical forces induced by flagellar motion. The process in which living microorganisms search for food and run away from poison chemicals is known is chemotaxy. Optical tweezers can be used to obtain a better understanding of chemotaxy by observing the force response of the microorganism when placed in a gradient of attractors and or repelling chemicals. This report shows such observations for the protozoa Leishmania amazomenzis, responsible for the leishmaniasis, a serious tropical disease. We used a quadrant detector to monitor the movement of the protozoa for different chemicals gradient. This way we have been able to observe both the force strength and its directionality. The characterization of the chemotaxis of these parasites can help to understand the infection mechanics and improve the diagnosis and the treatments employed for this disease.

  13. Goddard Robotic Telescope - Optical Follow-up of GRBs and Coordinated Observations of AGNs

    Science.gov (United States)

    Sakamoto, T.; Wallace, C. A.; Donato, D.; Gehrels, N.; Okajima, T.; Ukwatta, T. N.

    2010-01-01

    Since it is not possible to predict when a Gamma-Ray Burst (GRB) will occur or when Active Galactic Nucleus (AGN) flaring activity starts, follow-up/monitoring ground telescopes must be located as uniformly as possible all over the world in order to collect data simultaneously with Fermi and Swift detections. However, there is a distinct gap in follow-up coverage of telescopes in the eastern U.S. region based on the operations of Swift. Motivated by this fact, we have constructed a 14" fully automated optical robotic telescope, Goddard Robotic Telescope (GRT), at the Goddard Geophysical and Astronomical Observatory. The aims of our robotic telescope are 1) to follow-up Swift/Fermi GRBs and 2) to perform the coordinated optical observations of Fermi Large Area Telescope (LAT) AGN. Our telescope system consists of off-the-shelf hardware. With the focal reducer, we are able to match the field of view of Swift narrow instruments (20' x 20'). We started scientific observations in mid-November 2008 and GRT has been fully remotely operated since August 2009. The 3(sigma) upper limit in a 30-second exposure in the R filter is approx.15.4 mag; however, we can reach to approx.18 mag in a 600-second exposures. Due to the weather condition at the telescope site. our observing efficiency is 30-40%, on average.

  14. Simultaneous infrared and optical observations of the transiting debris cloud around WD 1145+017

    CERN Document Server

    Zhou, G; Bailey, J; Marshall, J P; Bayliss, D D R; Stockade, C; Nelson, P; Tan, T G; Rodriguez, J E; Tinney, C G; Dragomir, D; Colon, K; Shporer, A; Bento, J; Sefako, R; Horne, K; Cochran, W

    2016-01-01

    We present multi-wavelength photometric monitoring of WD 1145+017, a white dwarf exhibiting periodic dimming events interpreted to be the transits of orbiting, disintegrating planetesimals. Our observations include the first set of near-infrared light curves for the object, obtained on multiple nights over the span of one month, and recorded multiple transit events with depths ranging from ~20% to 50%. Simultaneous near-infrared and optical observations of the deepest and longest duration transit event were obtained at two epochs with the Anglo-Australian Telescope and three optical facilities, over the wavelength range of 0.5-1.2 microns. These observations revealed no measurable difference in transit depths for multiple photometric pass bands, allowing us to place a 2 sigma lower limit of 0.8 microns on the grain size in the putative transiting debris cloud. The lack of small grains is consistent with the infrared excess about the white dwarf, and may point towards a collision-dominated debris disc.

  15. Estimating dissolved organic carbon concentration in turbid coastal waters using optical remote sensing observations

    Science.gov (United States)

    Cherukuru, Nagur; Ford, Phillip W.; Matear, Richard J.; Oubelkheir, Kadija; Clementson, Lesley A.; Suber, Ken; Steven, Andrew D. L.

    2016-10-01

    Dissolved Organic Carbon (DOC) is an important component in the global carbon cycle. It also plays an important role in influencing the coastal ocean biogeochemical (BGC) cycles and light environment. Studies focussing on DOC dynamics in coastal waters are data constrained due to the high costs associated with in situ water sampling campaigns. Satellite optical remote sensing has the potential to provide continuous, cost-effective DOC estimates. In this study we used a bio-optics dataset collected in turbid coastal waters of Moreton Bay (MB), Australia, during 2011 to develop a remote sensing algorithm to estimate DOC. This dataset includes data from flood and non-flood conditions. In MB, DOC concentration varied over a wide range (20-520 μM C) and had a good correlation (R2 = 0.78) with absorption due to coloured dissolved organic matter (CDOM) and remote sensing reflectance. Using this data set we developed an empirical algorithm to derive DOC concentrations from the ratio of Rrs(412)/Rrs(488) and tested it with independent datasets. In this study, we demonstrate the ability to estimate DOC using remotely sensed optical observations in turbid coastal waters.

  16. Field and material stresses predict observable surface forces in optical and electrostatic manipulation

    Science.gov (United States)

    Kemp, Brandon A.; Sheppard, Cheyenne J.

    2016-09-01

    The momentum of light in media has been one of the most debated topics in physics over the past one hundred years. Originally a theoretical debate over the electrodynamics of moving media, practical applications have emerged over the past few decades due to interest in optical manipulation and nanotechnology. Resolution of the debate identifies a kinetic momentum as the momentum of the fields responsible for center of mass translations and a canonical momentum related to the coupled field and material system. The optical momentum resolution has been considered incomplete because it did not uniquely identify the full stress-energy-momentum (SEM) tensor of the field-kinetic subsystem. A consequence of this partial resolution is that the field-kinetic momentum could be described by three of the leading formulations found in the literature. The Abraham, Einstein-Laub, and Chu SEM tensors share the field-kinetic momentum, but their SEM tensors differ resulting in competing force densities. We can show now that the Abraham and Einstein-Laub formulations are invalid since their SEM tensors are not frame invariant, whereas the Chu SEM tensor satisfies relativistic principles as the field-kinetic formulation. However, a number of reports indicate that the force distribution in matter may not accurately represent experimental observations. In this correspondence, we show that the field-kinetic SEM tensor can be used along with the corresponding material subsystem to accurately predict experimental force and stress distributions. We model experimental examples from optical and static manipulation of particles and fluids.

  17. Type IIn Supernova SN 2010jl: Optical Observations for Over 500 Days After Explosion

    CERN Document Server

    Zhang, Tianmeng; Wu, Chao; Chen, Juncheng; Chen, Jia; Liu, Qin; Huang, Fang; Liang, Jide; Zhao, Xulin; Li, Lin; Wang, Min; Dennefeld, Michel; Zhang, Jujia; Zhai, Meng; Wu, Hong; Fan, Zhou; Zou, Hu; Zhou, Xu; Ma, Jun

    2012-01-01

    We present extensive optical observations of a Type IIn supernova (SN) 2010jl for the first 1.5 years after the discovery. The UBVRI light curves demonstrated an interesting two-stage evolution during the nebular phase, which almost flatten out after about 90 days from the optical maximum. SN 2010jl has one of the highest intrinsic H_alpha luminosity ever recorded for a SN IIn, especially at late phase, suggesting a strong interaction of SN ejecta with the dense circumstellar material (CSM) ejected by the progenitor. This is also indicated by the remarkably strong Balmer lines persisting in the optical spectra. One interesting spectral evolution about SN 2010jl is the appearance of asymmetry of the Balmer lines. These lines can be well decomposed into a narrow component and an intermediate-width component. The intermediate-width component showed a steady increase in both strength and blueshift with time until t ~ 400 days after maximum, but it became less blueshifted at t ~ 500 days when the line profile appe...

  18. Optical follow-up observations of Locburst GRB locations with OMC test camera

    Science.gov (United States)

    Rezek, Tomás

    1999-01-01

    The test camera of the Optical Monitoring Camera (OMC) experiment for INTEGRAL spacecraft achieving the angular pixel size of 18 arcsec and the field of view 7.5 degx5.1 deg has been succesfully developed and tested at the Astronomical Institute Ondrejov. The test camera is able to provide imaging down to 15 mag over the whole field of view within one exposure of 300 seconds. Although developed primarily to test the OMC performance and help with software development, this device is ideally suitable for the use as ground-based camera for the sites where Compton Gamma-Ray Observatory BATSE Locburst triggers are followed-up in optical waveband and also for widefield sky monitoring in general. The low cost of this camera makes it possible to duplicate the system to a number of observing sites. A chart and a corresponding CCD-image for the BACODINE Locburst Position 6368 taken with OMC test camera at Ondrejov observatory are also presented. The image taken 18 hours after the trigger was computer-blinked with the frame taken 30 days later. No optical activity has been found down to 13.5 mag.

  19. First gravitational-wave burst GW150914: MASTER optical follow-up observations

    Science.gov (United States)

    Lipunov, V. M.; Kornilov, V.; Gorbovskoy, E.; Buckley, D. A. H.; Tiurina, N.; Balanutsa, P.; Kuznetsov, A.; Greiner, J.; Vladimirov, V.; Vlasenko, D.; Chazov, V.; Kuvshinov, D.; Gabovich, A.; Potter, S. B.; Kniazev, A.; Crawford, S.; Rebolo Lopez, R.; Serra-Ricart, M.; Israelian, G.; Lodieu, N.; Gress, O.; Budnev, N.; Ivanov, K.; Poleschuk, V.; Yazev, S.; Tlatov, A.; Senik, V.; Yurkov, V.; Dormidontov, D.; Parkhomenko, A.; Sergienko, Yu.; Podesta, R.; Levato, H.; Lopez, C.; Saffe, C.; Podesta, F.; Mallamaci, C.

    2017-03-01

    The Advanced LIGO observatory recently reported the first direct detection of the gravitational waves (GWs) predicted by Einstein & Sitzungsber. We report on the first optical observations of the GW source GW150914 error region with the Global MASTER Robotic Net. Between the optical telescopes of electromagnetic support, the covered area is dominated by MASTER with an unfiltered magnitude up to 19.9 mag (5σ). We detected several optical transients, which proved to be unconnected with the GW event. The main input to investigate the final error box of GW150914 was made by the MASTER-SAAO robotic telescope, which covered 70 per cent of the final GW error box and 90 per cent of the common localization area of the LIGO and Fermi events. Our result is consistent with the conclusion (Abbott et al. 2016a) that GWs from GW150914 were produced in a binary black hole merger. At the same time, we cannot exclude that MASTER OT J040938.68-541316.9 exploded on 2015 September 14.

  20. Comparison of optical observational capabilities for the coming decades: ground versus space

    CERN Document Server

    Mountain, Matt; Soummer, Remi; Koekemoer, Anton; Ferguson, Harry; Postman, Marc; Gavel, Donald T; Guyon, Olivier; Simons, Douglas; Traub, Wesley A

    2009-01-01

    Ground-based adaptive optics (AO) in the infrared has made exceptional advances in approaching space-like image quality at higher collecting area. Optical-wavelength applications are now also growing in scope. We therefore provide here a comparison of the pros and cons of observational capabilities from the ground and from space at optical wavelengths. With an eye towards the future, we focus on the comparison of a ~30m ground-based telescope with an 8-16m space-based telescope. We review the current state-of-the-art in AO, and summarize the expected future improvements in image quality, field of view, contrast, and low-wavelength cut-off. We discuss the exciting advances in extreme AO for exoplanet studies and explore what the theoretical limitations in achievable contrast might be. Our analysis shows that extreme AO techniques face both fundamental and technological hurdles to reach the contrast of 1E-10 necessary to study an Earth-twin at 10 pc. Based on our assessment of the current state-of-the-art, the ...

  1. Deep optical observations of unusual neutron star Calvera with the GTC

    CERN Document Server

    Shibanov, Yury; Zharikov, Sergey; Shternin, Peter; Zyuzin, Dima

    2016-01-01

    Calvera is an unusual isolated neutron star with pure thermal X-ray spectrum typical for central compact objects in supernova remnants. On the other hand, its rotation period and spin-down rate are typical for ordinary rotation-powered pulsars. It was discovered and studied in X-rays and not yet detected in other spectral domains. We present deep optical imaging of the Calvera field obtained with the Gran Telescopio Canarias in $g'$ and $i'$ bands. Within $\\approx 1^{\\prime\\prime}$ vicinity of Calvera, we detected two point-like objects invisible at previous shallow observations. However, accurate astrometry showed that none of them can be identified with the pulsar. We put new upper limits on its optical brightness of $g' > 27.87$ and $i' > 26.84$. We also reanalyzed all available archival X-ray data on Calvera. Comparison of the Calvera thermal emission parameters and upper limits on optical and non-thermal X-ray emission with respective data on rotation-powered pulsars shows that Calvera might belong to th...

  2. Observation of Defect-Free Surface Modes in Optical Waveguide Arrays

    Science.gov (United States)

    Szameit, Alexander; Garanovich, Ivan L.; Heinrich, Matthias; Sukhorukov, Andrey A.; Dreisow, Felix; Pertsch, Thomas; Nolte, Stefan; Tünnermann, Andreas; Kivshar, Yuri S.

    2008-11-01

    We report on the experimental observation of novel defect-free surface modes predicted theoretically for modulated photonic lattices [I. L. Garanovich et al., Phys. Rev. Lett. 100, 203904 (2008)PRLTAO0031-900710.1103/PhysRevLett.100.203904]. We generate the linear surface modes in truncated arrays of periodically curved optical waveguides created in fused silica by a laser direct-writing technique. Our results demonstrate that the degree of surface wave localization can be controlled by selecting the waveguide bending amplitude.

  3. Managing GRB afterglows optical/IR observations in the web 2.0 era

    Science.gov (United States)

    Ricci, D.; Nicastro, L.

    2013-07-01

    We present an overview of top internet technologies that can be used to build webtools and rich internet applications for astronomy. The aim is to simplify the data handling, reduction and access, in particular of optical/infrared images collected by traditional, automatic or robotic telescopes. These tools are particularly suitable for real-time management of GRB afterglow observations. Using these technologies we are developing a web-based images database management system. We present available features and discuss further improvements to the mentioned system.

  4. Study on Geomagnetic Space Observatories

    DEFF Research Database (Denmark)

    Bak, Thomas; Blanke, M.; Wisniewski, Rafal

    1996-01-01

    Magnetometry was one of the objectives of the Aristoteles mission endorsed at the 1991 Earth Observation User Consultation meeting.......Magnetometry was one of the objectives of the Aristoteles mission endorsed at the 1991 Earth Observation User Consultation meeting....

  5. Study on Geomagnetic Space Observatories

    DEFF Research Database (Denmark)

    Bak, Thomas; Blanke, M.; Wisniewski, Rafal

    1996-01-01

    Magnetometry was one of the objectives of the Aristoteles mission endorsed at the 1991 Earth Observation User Consultation meeting.......Magnetometry was one of the objectives of the Aristoteles mission endorsed at the 1991 Earth Observation User Consultation meeting....

  6. Phytoplankton, sediment and optical observations in Netherlands coastal water in spring

    Science.gov (United States)

    Wild-Allen, Karen; Lane, Andrew; Tett, Paul

    2002-06-01

    Factors controlling the dynamics of suspended particulate matter (SPM), its influence on sea-leaving radiance and in-water optical properties, and the consequences of optical variation for phytoplankton growth, were studied at the 'Processes of Vertical Exchange in Shelf Seas' (PROVESS) project's southern North Sea site during April 1999. The optical properties of Netherlands coastal water were not unexpectedly found to be primarily determined by suspended sediment (Case 2) and were classified as Jerlov type 7 'relatively turbid coastal water'. During the study period, vertical mixing periodically resuspended optically active particles from the bed fluff layer throughout the water column and into the near-surface layer. These particles influenced sea surface radiance reflectance, and the red/green ratio of radiance reflectance, both of which can be observed by remote sensing. Linear relationships between sea surface radiance reflectance and SPM concentration were primarily determined by the inorganic fraction, as organic SPM varied little in concentration throughout the cruise period. The inorganic fraction was an important scatterer of light at all wavelengths, whereas the organic fraction displayed a greater tendency for light absorption at shorter wavelengths. Although the euphotic layer (depth of 1% surface irradiance) was only 8-10 m deep, vertical mixing ensured that phytoplankton throughout the water column (˜18 m) had access to PAR in excess of the estimated compensation illumination. Growth rates of microplankton (which includes pelagic microheterotrophs as well as phytoplankters) were calculated using an algorithm from the PROWQM model. These ranged from 0.1 to 0.3 d -1, and implied loss rates of 3-25% which were mostly attributed to mesozooplankton grazing. Estimated oxygen production, however, was in near equilibrium with oxygen demand observed in dark bottles, and implied a significant oxygen demand due to detrital respiration and nitrification. This

  7. Generation of different long-period geomagnetic pulsations during a sudden impulse

    Science.gov (United States)

    Moiseyev, A. V.; Popov, V. I.; Mullayarov, V. A.; Samsonov, S. N.; Du, A.; Yoshikawa, A.

    2015-07-01

    The space-time characteristics of geomagnetic pulsations during a sudden impulse on August 4, 2010 have been analyzed using ground-based and satellite observations. It has been indicated that two types of geomagnetic pulsations with different spatial extensions, oscillation frequencies, and generations were observed at that time. It has been found that geomagnetic pulsations with identical oscillation frequencies (˜4.5 mHz) at different latitudes were observed, with a maximal amplitude in the dusk sector. Oscillations with close frequencies were registered in the solar wind in the IMF B z component. Higher-frequency (7-10 mHz) pulsations dependent on latitude were registered on the dawn side. It is assumed that geomagnetic pulsations with frequencies of ˜4.5 mHz were caused by oscillations penetrating from the interplanetary medium, and higher-frequency pulsations were Alfvén resonance oscillations generated during the compression of the magnetosphere. An asymmetric oscillation amplitude distribution relative to noon was caused by the IMF orthospiral orientation in this event.

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

    Science.gov (United States)

    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.

  9. [Results from the X-ray and Optical Follow-up Observations of the Swift BAT AGN Survey

    Science.gov (United States)

    Mushotzky, R.

    2008-01-01

    I will present results from the x-ray and optical follow-up observations of the Swift BAT ACN survey. I will discuss the nature of obscuration in these objects, the relationship to optical properties and the change of properties with luminosity and galaxy type and how they will influence the design of XO.

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

    Science.gov (United States)

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

    2016-09-01

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

  11. Characterization and diagnostic methods for geomagnetic auroral infrasound waves

    Science.gov (United States)

    Oldham, Justin J.

    Infrasonic perturbations resulting from auroral activity have been observed since the 1950's. In the last decade advances in infrasonic microphone sensitivity, high latitude sensor coverage, time series analysis methods and computational efficiency have elucidated new types of auroral infrasound. Persistent periods of infrasonic activity associated with geomagnetic sub-storms have been termed geomagnetic auroral infrasound waves [GAIW]. We consider 63 GAIW events recorded by the Fairbanks, AK infrasonic array I53US ranging from 2003 to 2014 and encompassing a complete solar cycle. We make observations of the acoustic features of these events alongside magnetometer, riometer, and all-sky camera data in an effort to quantify the ionospheric conditions suitable for infrasound generation. We find that, on average, the generation mechanism for GAIW is confined to a region centered about ~60 0 longitude east of the anti-Sun-Earth line and at ~770 North latitude. We note furthermore that in all cases considered wherein imaging riometer data are available, that dynamic regions of heightened ionospheric conductivity periodically cross the overhead zenith. Consistent features in concurrent magnetometer conditions are also noted, with irregular oscillations in the horizontal component of the field ubiquitous in all cases. In an effort to produce ionosphere based infrasound free from the clutter and unknowns typical of geophysical observations, an experiment was undertaken at the High Frequency Active Auroral Research Program [HAARP] facility in 2012. Infrasonic signals appearing to originate from a source region overhead were observed briefly on 9 August 2012. The signals were observed during a period when an electrojet current was presumed to have passed overhead and while the facilities radio transmitter was periodically heating the lower ionosphere. Our results suggest dynamic auroral electrojet currents as primary sources of much of the observed infrasound, with

  12. Deep Optical Observations of Unusual Neutron Star Calvera with the GTC

    Science.gov (United States)

    Shibanov, Yury; Danilenko, Andrey; Zharikov, Sergey; Shternin, Peter; Zyuzin, Dima

    2016-11-01

    Calvera is an unusual, isolated neutron star with a pure thermal X-ray spectrum typical of central compact objects in supernova remnants. On the other hand, its rotation period and spin-down rate are typical of ordinary rotation-powered pulsars. It was discovered and studied through X-rays, and has not yet been detected in other spectral domains. We present deep optical imaging of the Calvera field, obtained with the Gran Telescopio Canarias, in the g\\prime and i\\prime bands. Within the vicinity of ≈ 1\\prime\\prime of Calvera, we detected two point-like objects that were invisible at previous shallow observations. However, accurate astrometry showed that neither of them can be identified with the pulsar. We put new upper limits of g\\prime \\gt 27.87 and i\\prime \\gt 26.84 on its optical brightness. We also reanalyzed all available archival X-ray data on Calvera. Comparison of the Calvera thermal emission parameters and upper limits on optical and non-thermal X-ray emission with respective data on rotation-powered pulsars shows that Calvera might belong to the class of ordinary middle-aged pulsars, if we assume that its distance is in the range of 1.5-5 kpc. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, on the island of La Palma, program GTC1-14AMEX.

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

    Science.gov (United States)

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

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

  14. Comparison of Dst Forecast Models for Intense Geomagnetic Storms

    Science.gov (United States)

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

    2012-01-01

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

  15. Large Geomagnetic Storms Associated with Limb Halo Coronal Mass Ejections

    CERN Document Server

    Gopalswamy, Nat; Xie, Hong; Akiyama, Sachiko; Makela, Pertti

    2009-01-01

    Solar cycle 23 witnessed the observation of hundreds of halo coronal mass ejections (CMEs), thanks to the high dynamic range and extended field of view of the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO) mission. More than two thirds of halo CMEs originating on the front side of the Sun have been found to be geoeffective (Dst = 45deg) have a 20% shorter delay time on the average. It was suggested that the geomagnetic storms due to limb halos must be due to the sheath portion of the interplanetary CMEs (ICMEs) so that the shorter delay time can be accounted for. We confirm this suggestion by examining the sheath and ejecta portions of ICMEs from Wind and ACE data that correspond to the limb halos. Detailed examination showed that three pairs of limb halos were interacting events. Geomagnetic storms following five limb halos were actually produced by other disk halos. The storms followed by four isolated limb halos and the ones associated with interact...

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

    Science.gov (United States)

    Stauning, Peter

    2013-06-01

    The strong geomagnetic storm in the evening of 30 October 2003 caused high-voltage power grid disturbances in Sweden that expanded to produce hour-long power line outage in Malmö located in the southern part of the country. This was not a unique situation. The geomagnetic storm on 13 March 1989 caused extensive disruptions of high-voltage power circuits especially in the Province of Quebec, Canada, but also to a lesser degree in Scandinavia. Similar events have occurred earlier, among others, during the great storms of 13-14 July 1982 and 8-9 February 1986. These high-voltage power grid disturbances were related to impulsive magnetic variations accompanying extraordinarily intense substorm events. The events were preceded by lengthy intervals of unusually high values of the Polar Cap (PC) index caused by enhanced transpolar ionospheric convection. The transpolar convection transports magnetic flux from the dayside to nightside which causes equatorward displacements of the region of auroral activity enabling the substorms to hit vital power grids. During the 30 October 2003 event the intense solar proton radiation disabled the ACE satellite observations widely used to provide forecast of magnetic storm events. Hence in this case the alarmingly high PC index could provide useful warning of the storm as a back-up of the missing ACE-based forecast. In further cases, monitoring the PC index level could provide supplementary storm warnings to the benefit of power grid operators.

  17. Geomagnetic response to IMF and solar wind over different latitudes

    Science.gov (United States)

    Aslam, A. M.; Tripathi, Sharad Chandra; Mansoori, Azad Ahmad; Waheed, Malik Abdul

    2016-07-01

    In this paper a study on the response of geomagnetic field characteristics to the solar wind variation during three solar cycles (SC 21, SC 22, SC 23) have been conducted in a long term scale. The difference in the response of two different latitudinal characteristic indices has been investigated. For the purpose we have considered the high latitude index AE and the mid-latitude aa index and both gives the knowledge about the perturbations in the geomagnetic field conditions. Eventually we can infer the idea about the ionospheric current system changes in response to the solar wind conditions. The variation found in the AE and aa indices have been found to follow a 11 year cycle as similar to the sunspot variation. Also the correlation between the annual means of the solar wind parameters velocity V, magnetic filed B and the composite parameters BV and BV ^{2 } have been calculated . A difference was found between the correlations obtained for the AE and aa indices. We could also see that the difference in correlation follows a cyclic pattern i.e. the large difference is found during the solar maxima while a small difference is observed during the minima.

  18. MagIC: Geomagnetic Applications from Earth History to Archeology

    Science.gov (United States)

    Constable, C.; Tauxe, L.; Koppers, A.; Minnett, R.; Jarboe, N.

    2016-12-01

    Major scientific challenges increasingly require an interdisciplinary approach, and highlight the need for open archives, incorporating visualization and analysis tools that are flexible enough to address novel research problems. Increasingly modern standards for publication are (or should be) demanding direct links to data, data citations, and adequate documentation that allow other researchers direct access to the fundamental measurements and analyses producing the results. Carefully documented metadata are essential and data models may need considerable complexity to accommodate re-use of observations originally collected with a different purpose in mind. The Magnetics Information Consortium (MagIC) provides an online home for all kinds of paleo-, archeo-magnetic, rock, and environmental magnetic data, from documentation of fieldwork, through lab protocols, to interpretations in terms of geomagnetic history. Examples of their application to understanding geomagnetic field behavior, archeological dating, and voyages of exploration to discover America will be used to highlight best practices and illustrate unexpected benefits of data archived using best practices with the goal of maintaining high standards for reproducibility.

  19. Geomagnetic core field models in the satellite era

    DEFF Research Database (Denmark)

    Lesur, Vincent; Olsen, Nils; Thomson, Alan W. P.

    2011-01-01

    After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case ...... only up to degree 8 or 9. For higher time derivatives of core field models, only the very first degrees are robustly derived.......After a brief review of the theoretical basis and difficulties that modelers are facing, we present three recent models of the geomagnetic field originating in the Earth’s core. All three modeling approaches are using recent observatory and near-Earth orbiting survey satellite data. In each case...... the specific aims and techniques used by the modelers are described together with a presentation of the main results achieved. The three different modeling approaches are giving similar results. For a snap shot of the core magnetic field at a given epoch and observed at the Earth’s surface, the differences...

  20. Driving Plasmaspheric Electron Density Simulations During Geomagnetic Storms

    Science.gov (United States)

    De Pascuale, S.; Kletzing, C.; Jordanova, V.; Goldstein, J.; Wygant, J. R.; Thaller, S. A.

    2015-12-01

    We test global convection electric field models driving plasmaspheric electron density simulations (RAM-CPL) during geomagnetic storms with in situ measurements provided by the Van Allen Probes (RBSP). RAM-CPL is the cold plasma component of the ring-current atmosphere interactions suite (RAM-SCB) and describes the evolution of plasma density in the magnetic equatorial plane near Earth. Geomagnetic events observed by the RBSP satellites in different magnetic local time (MLT) sectors enable a comparison of local asymmetries in the input electric field and output densities of these simulations. Using a fluid MHD approach, RAM-CPL reproduces core plasmaspheric densities (L<4) to less than 1 order of magnitude difference. Approximately 80% of plasmapause crossings, defined by a low-density threshold, are reproduced to within a mean radial difference of 0.6 L. RAM-CPL, in conjunction with a best-fit driver, can be used in other studies as an asset to predict density conditions in locations distant from RBSP orbits of interest.

  1. Solar Microwave and Geomagnetic Field Pulsations as Space Weather Factors

    Science.gov (United States)

    Snegirev, S. D.; Fridman, V. M.; Sheiner, O. A.

    The procedure of short-term prediction of main solar flares was created on the basis of temporal behavior of long-period microwave pulsations [Kobrin et al., 1997]. At the same time it was shown that before these flares one could observe long-period (T > 20 min) pulsations of geomagnetic field [Kobrin et al, 1985]. The resemblance between microwave and geomagnetic pulsations (duration and temporal behaviour) allows us to propose the common nature of these variations: the reflection of solar energy accumulation and instabilities in solar centers of activity. To be an important factor of Space Weather above mentioned pulsations can be useful for constructing the procedures to predict the near Earth's conditions. This work was supported by the Russian Foundation for Fundamental Research and Russian Federal Programm "Astronomy" (grant N 1.5.5.5). Kobrin M.M, Malygin V.I., Snegirev S.D. Plan. Space Sci., 33, N11, p. 1251 (1985). Kobrin M.M., Pakhomov V.V., Snegirev S.D., Fridman V.M., Sheiner O.A. Proc. Workshop `STPW-96', Tokyo: RCW, p. 200 (1997).

  2. Simultaneous optical/gamma-ray observations of GRB 121217's prompt emission

    CERN Document Server

    Elliott, J; Schmidl, S; Greiner, J; Gruber, D; Oates, S; Kobayashi, S; Zhang, B; Cummings, J R; Filgas, R; Gehrels, N; Grupe, D; Kann, D A; Klose, S; Krühler, T; Guelbenzu, A Nicuesa; Rau, A; Rossi, A; Siegel, M; Schady, P; Sudilovsky, V; Tanga, M; Varela, K

    2013-01-01

    Since the advent of the Swift satellite it has been possible to obtain precise localisations of GRB positions of sub-arcsec accuracy within seconds, facilitating ground-based robotic telescopes to automatically slew to the target within seconds. This has yielded a plethora of observational data for the afterglow phase of the GRB, but the quantity of data (<2 keV) covering the initial prompt emission still remains small. Only in a handful of cases has it been possible obtain simultaneous coverage of the prompt emission in a multi-wavelength regime (gamma-ray to optical), as a result of: observing the field by chance prior to the GRB (e.g. 080319B/naked-eye burst), long-prompt emission (e.g., 080928, 110205A) or triggered on a pre-cursor (e.g., 041219A, 050820A, 061121). This small selection of bursts have shown both correlated and uncorrelated gamma-ray and optical light curve behaviour, and the multi-wavelength emission mechanism remains far from resolved (i.e. single population synchrotron self-Component,...

  3. Near-UV and optical observations of the transiting exoplanet TrES-3b

    CERN Document Server

    Turner, Jake D; Hardegree-Ullman, Kevin K; Carleton, Timothy M; Walker-LaFollette, Amanda M; Crawford, Benjamin E; Smith, Carter-Thaxton W; McGraw, Allison M; Small, Lindsay C; Rocchetto, Marco; Cunningham, Kathryn I; Towner, Allison P M; Zellem, Robert; Robertson, Amy N; Guvenen, Blythe C; Schwarz, Kamber R; Hardegree-Ullman, Emily E; Collura, Daniel; Henz, Triana N; Lejoly, Cassandra; Richardson, Logan L; Weinand, Michael A; Taylor, Joanna M; Daugherty, Michael J; Wilson, Ashley A; Austin, Carmen L

    2012-01-01

    We observed nine primary transits of the hot Jupiter TrES-3b in several optical and near-UV photometric bands from 2009 June to 2012 April in an attempt to detect its magnetic field. Vidotto, Jardine and Helling suggest that the magnetic field of TrES-3b can be constrained if its near-UV light curve shows an early ingress compared to its optical light curve, while its egress remains unaffected. Predicted magnetic field strengths of Jupiter-like planets should range between 8 G and 30 G. Using these magnetic field values and an assumed B_star of 100 G, the Vidotto et al. method predicts a timing difference of 5-11 min. We did not detect an early ingress in our three nights of near-UV observations, despite an average cadence of 68 s and an average photometric precision of 3.7 mmag. However, we determined an upper limit of TrES-3b's magnetic field strength to range between 0.013 and 1.3 G (for a 1-100 G magnetic field strength range for the host star, TrES-3) using a timing difference of 138 s derived from the N...

  4. RXTE Observations of the Vela Pulsar The X-ray-Optical Connection

    CERN Document Server

    Harding, A K; Gwinn, C R; McCulloch, P M; Moffet, D; Harding, Alice K; Strickman, Mark S.; Gwinn, Carl

    1999-01-01

    We report on our analysis of a 300 ks observation of the Vela pulsar with the Rossi X-Ray Timing Explorer (RXTE). The double-peaked, pulsed emission at 2 - 30 keV, which we had previously detected during a 93 ks observation, is confirmed with much improved statistics. There is now clear evidence, both in the spectrum and the light curve, that the emission in the RXTE band is a blend of two separate components. The spectrum of the harder component connects smoothly with the OSSE, COMPTEL and EGRET spectrum and the peaks in the light curve are in phase coincidence with those of the high-energy light curve. The spectrum of the softer component is consistent with an extrapolation to the pulsed optical flux, and the second RXTE pulse is in phase coincidence with the second optical peak. In addition, we see a peak in the 2-8 keV RXTE pulse profile at the radio phase.

  5. Near-uv and optical observations of the transiting hot Jupiter WASP-1b

    Science.gov (United States)

    Pearson, K. A.; Zellem, R.; Biddle, L. I.; Amaya, H.; Watson, Z.; Griffith, C.; Small, L.; Hume, J.

    2014-03-01

    We present simultaneous near-UV (U-band) and optical (B-band) photometric observations of the primary transit of the highly irradiated, hot-Jupiter WASP-1b on the Kuiper 61" telescope. We use our results to search for timing transit variations, which would indicate additional planets, and provide new constraints on WASP-1b's physical parameters. Assuming the opacity at these two photometric bands is dominated by Rayleigh scattering by molecular hydrogen, we can place strong upper limits on its radius. Such constraints can limit the degeneracy between an exoplanet's physical radius and atmospheric composition in radiative transfer retrievals. Additionally its host star is chromospherically active and WASP-1b orbits within in the co-rotation radius of the star making it likely that WASP-1b has a bowshock. Therefore, we will search for a planetary magnetic field as indicated by an early ingress in the near-UV light curve compared to the optical due to the bowshock itself. Such measurements would confirm the observational methodology of detecting magnetic fields around transiting exoplanets, place an upper limit on WASP-1b's magnetic field strength, and confirm previous theoretical estimations of hot Jupiter magnetic fields.

  6. XMM-Newton and optical observations of the eclipsing polar CSS081231:071126+440405

    CERN Document Server

    Worpel, H

    2015-01-01

    Aims: We aim to study the temporal and spectral behaviour of the eclipsing polar CSS081231:071126+440405 from the infrared to the X-ray regime. Methods: We obtained phase-resolved XMM-Newton X-ray observations on two occasions in 2012 and 2013 in different states of accretion. In 2013 the XMM-Newton X-ray and UV data were complemented by optical photometric and spectroscopic observations. Results: CSS081231 displays two-pole accretion in the high state. The magnetic fields of the two poles are 36 and 69 MG, indicating a non-dipolar field geometry. The X-ray spectrum of the main accreting pole with the lower field comprises a hot thermal component from the cooling accretion plasma, $kT_{plas}$ of a few tens of keV, and a blackbody-like component from the accretion area with $kT_{rm bb} \\sim$ 50-100\\,eV. The high-field pole which was located opposite to the mass-donating star accretes at a low rate and has a plasma temperature of about 4\\,keV. At both occasions the X-ray eclipse midpoint precedes the optical ec...

  7. Suzaku and Multi-wavelength Observations of OJ 287 during the Periodic Optical Outburst in 2007

    CERN Document Server

    Seta, Hiromi; Tashiro, Makoto S; Yaji, Yuichi; Arai, Akira; Fukuhara, Masayuki; Kohno, Kotaro; Nakanishi, Koichiro; Sasada, Mahito; Shimajiri, Yoshito; Tosaki, Tomoka; Uemura, Makoto

    2009-01-01

    Suzaku observations of the blazar OJ 287 were performed in 2007 April 10--13 and November 7--9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be Gamma = 1.65 +- 0.02 and S_{1 keV} = 215 +- 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum (Gamma = 1.50 +- 0.01) with a nearly doubled X-ray flux density S_{1 keV} = 404^{+6}_{-5} nJy. Moreover, significant hard X-ray signals were detected up to ~ 27 keV. In cooperation with the Suzaku, simultaneous radio, optical, and very-high-energy gamma-ray observations were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 +- 0.46 Jy and 8.93 +- 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found to be higher by a factor of...

  8. A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift

    CERN Document Server

    Wu, Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P; Gronwall, Caryl; Wesolowski, Sarah; Porterfield, Blair L

    2012-01-01

    We have compiled a catalog of optically-selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both UVOT and XRT observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~60% which rises to ~85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about 0.3 dex to the quasar luminosity. We re-visit the alpha_ox-L_uv relation by selecting a clean sample with only type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared to studies that use non-simultaneous UV/opt...

  9. Confronting Simulations of Optically Thick Gas in Massive Halos with Observations at z=2-3

    CERN Document Server

    Fumagalli, Michele; Prochaska, J Xavier; Kasen, Daniel; Dekel, Avishai; Ceverino, Daniel; Primack, Joel

    2013-01-01

    We use high resolution hydrodynamic simulations to study the predicted distribution of neutral hydrogen around 21 galaxies in the halo mass range M_vir~3x10^11-4x10^12 M_sun at z~2. The covering fraction of optically-thick gas interior to the virial radius varies between f_c~0.05-0.2, with significant scatter among halos. Contrary to recent claims, both the mass fraction of cold (T= 10^12M_sun underpredict the covering fraction of optically-thick gas observed in the environs of quasar host galaxies by a large factor. The reasons for this discrepancy, possibly related to the treatment of feedback and hydrodynamic instability in simulations or to the fact that quasars may represent a special phase in the life of a galaxy, remain unclear. Conversely, we do not find statistically significant difference between the predicted covering fraction and observations in the lower mass halos M_vir>=5x10^11 M_sun hosting Lyman break galaxies. However, current samples of quasar-galaxy pairs are too small for conclusive compa...

  10. X-Ray and Optical Observations of A 0535+26

    CERN Document Server

    Camero-Arranz, A; Wilson-Hodge, C A; Jenke, P; Steele, I; Coe, M J; Gutierrez-Soto, J; Kretschmar, P; Caballero, I; Case, G; Cherry, M L; Yan, J; Suso, J; Rodríguez, J; Guiriec, S; McBride, V A

    2011-01-01

    We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A 0535+26 with the Fermi/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the context of the rich historical data and discussed in terms of the neutron star Be-disk interaction. The Be circumstellar disk was exceptionally large just before the 2009 December giant outburst, which may explain the origin of the unusual recent X-ray activity of this source. We found a peculiar evolution of the pulse profile during this giant outburst, with the two main components evolving in opposite ways with energy. A hard 30-70 mHz X-ray QPO was detected with GBM during this 2009 December giant outburst. It becomes stronger with increasing energy and disappears at energies below 25 keV. In the long-term a strong optical/X-ray correlation was found for this system, however in the medium-term the H{\\alpha} EW and the V-band brightness showed an anti-correlation after \\sim2002 Aug...

  11. X-ray and optical observations of M55 and NGC 6366: evidence for primordial binaries

    CERN Document Server

    Bassa, C G; Verbunt, F; Homer, L; Anderson, S F; Lewin, W H G

    2008-01-01

    We present Chandra X-ray Observatory ACIS-S3 X-ray imaging observations and VLT/FORS2 and Hubble Space Telescope optical observations of two low-density Galactic globular clusters; NGC 6366 and M55. We detect 16 X-ray sources with 0.5-6.0 keV luminosities above Lx=4E30 erg/s within the half-mass radius of M55, of which 8 or 9 are expected to be background sources, and 5 within the half-mass radius of NGC 6366, of which 4 are expected to be background sources. Optical counterparts are identified for several X-ray sources in both clusters and from these we conclude that 3 of the X-ray sources in M55 and 2 or 3 of the X-ray sources in NGC 6366 are probably related to the cluster. Combining these results with those for other clusters, we find the best fit for a predicted number of X-ray sources in a globular cluster Nc=1.2 Gamma+1.1 Mh, where Gamma is the collision number and Mh is (half of) the cluster mass, both normalized to the values for the globular cluster M4. Some sources tentatively classified as magneti...

  12. Observation of Zeeman shift in the rubidium D2 line using an optical nanofiber in vapor

    Science.gov (United States)

    Watkins, Amy; Tiwari, Vibhuti Bhushan; Ward, Jonathan M.; Deasy, Kieran; Nic Chormaic, Síle

    2013-11-01

    We report on the observation of a Zeeman shift (order of 100 MHz) of the Doppler-broadened D2 transition of both 85Rb and 87Rb isotopes via transmission through a 400 nm diameter optical nanofiber in the presence of a DC magnetic field. Linearly-polarized light propagating in the nanofiber is analyzed as a superposition of two orthogonally circularly polarized orientations, σ+ and σ-. In the absence of the magnetic field, the absorption of these polarizations by the atomic vapor, via the evanescent field at the waist of the nanofiber, is degenerate. When a weak magnetic field is applied parallel to the propagating light, this degeneracy is lifted and relative shifts in the resonance frequencies are detected. Typical linear shift rates of 1.6 MHz/G and -2.0 MHz/G were observed. We also demonstrate a dichroic atomic vapor laser lock line shape by monitoring the real-time subtraction of the two magnetically-shifted absorption spectra. This is particularly interesting for magneto-optical experiments as it could be directly implemented for diode laser frequencystabilization.

  13. Goddard Robotic Telescope - Optical Follow-up of GRBs and Coordinated Observations of AGNs -

    CERN Document Server

    Sakamoto, T; Donato, D; Gehrels, N; Okajima, T; Ukwatta, T N

    2010-01-01

    Since it is not possible to predict when a Gamma-Ray Burst (GRB) will occur or when Active Galactic Nucleus (AGN) flaring activity starts, follow-up/monitoring ground telescopes must be located as uniformly as possible all over the world in order to collect data simultaneously with Fermi and Swift detections. However, there is a distinct gap in follow-up coverage of telescopes in the eastern U.S. region based on the operations of Swift. Motivated by this fact, we have constructed a 14" fully automated optical robotic telescope, Goddard Robotic Telescope (GRT), at the Goddard Geophysical and Astronomical Observatory. The aims of our robotic telescope are 1) to follow-up Swift/Fermi GRBs and 2) to perform the coordinated optical observations of Fermi Large Area Telescope (LAT) AGN. Our telescope system consists of off-the-shelf hardware. With the focal reducer, we are able to match the field of view of Swift narrow instruments (20' x 20'). We started scientific observations in mid-November 2008 and GRT has been...

  14. Observation of Optical Solitons and Abnormal Modulation Instability in Liquid Crystals with Negative Dielectric Anisotropy

    CERN Document Server

    Wang, Jing; Chen, Junzhu; Liu, Jinlong; Wang, Zhuo; Li, Yiheng; Guo, Qi; Hu, Wei; Xuan, Li

    2015-01-01

    We investigate theoretically and experimentally the optical beam propagation in the nematic liquid crystal with negative dielectric anisotropy, which is aligned homeotropically in a $80\\mu m$-thickness planar cell in the presence of an externally voltage. It is predicted that the nonlocal nonlinearity of liquid crystal undergo an oscillatory response function with a negative nonlinear refractive index coefficient. We found that the oscillatory nonlocal nonlinearity can support stable bright solitons, which are observed in experiment. We also found that abnormal modulation instability occurs with infinity gain coefficient at a fixed spatial frequency, which is no depend on the beam intensity. We observed the modulation instability in the liquid crystal at a very low intensity ($0.26W/cm^2$), and the maximum gain frequency were found kept unchange when beam power changes over 2-3 orders of magnitude.

  15. Observation of the inverse Doppler effect in negative-index materials at optical frequencies

    Science.gov (United States)

    Chen, Jiabi; Wang, Yan; Jia, Baohua; Geng, Tao; Li, Xiangping; Feng, Lie; Qian, Wei; Liang, Bingming; Zhang, Xuanxiong; Gu, Min; Zhuang, Songlin

    2011-04-01

    The Doppler effect is a fundamental frequency shift phenomenon that occurs whenever a wave source and an observer are moving with respect to one another. It has well-established applications in astrophotonics, biological diagnostics, weather and aircraft radar systems, velocimetry and vibrometry. The counterintuitive inverse Doppler effect was theoretically predicted in 1968 by Veselago in negative-index materials. However, because of the tremendous challenges of frequency shift measurements inside such materials, most investigations of the inverse Doppler effect have been limited to theoretical predictions and numerical simulations. Indirect experimental measurements have been conducted only in nonlinear transmission lines at ~1-2 GHz (ref. 8) and in acoustic media at 1-3 kHz (ref. 9). Here, we report the first experimental observation of the inverse Doppler shift at an optical frequency (λ = 10.6 µm) by refracting a laser beam in a photonic-crystal prism that has the properties of a negative-index material.

  16. Optical interferometric observations of Theta 1 Orionis C from NPOI and implications for the system orbit

    CERN Document Server

    Patience, J; Prato, L; Franz, O; Wasserman, L; Tycner, C; Hutter, D J; Hummel, C A

    2008-01-01

    With the Navy Prototype Optical Interferometer (NPOI), the binary system Theta 1 Orionis C, the most massive member of the Trapezium, was spatially resolved over a time period extending from February 2006 to March 2007. The data show significant orbital motion over the 14 months, and, after combining the NPOI data with previous measurements of the system from the literature, the observations span 10 years of the orbit. Our results indicate that the secondary did not experience an unusually close periastron passage this year, in contradiction to the prediction of a recently published, highly eccentric ~11 year orbit. Future observations of this source will be required to improve the orbital solution. Possible implications of the results in terms of system distance are discussed, although a main conclusion of this work is that a definitive orbit solution will require more time to obtain sufficient phase coverage, and that the interaction effects expected at periastron did not occur in 2007.

  17. Surface magneto-optical and Mössbauer observations of Fe–Al

    Energy Technology Data Exchange (ETDEWEB)

    Jirásková, Y., E-mail: jirasko@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-61662 Brno (Czech Republic); Hendrych, A.; Životský, O. [Department of Physics, VŠB-Technical University of Ostrava, CZ-70833, Ostrava (Czech Republic); Nanotechnology Centre, VŠB-Technical University of Ostrava, CZ-70833 Ostrava (Czech Republic); Buršík, J.; Žák, T. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, CZ-61662 Brno (Czech Republic); Procházka, I. [Charles University in Prague, Faculty of Mathematic and Physics, Department of Low Temperature Physics, CZ-18000 Prague (Czech Republic); Janičkovič, D. [Institute of Physics, Slovak Academy of Sciences, SK-84511 Bratislava (Slovakia)

    2013-07-01

    The paper is devoted to detailed surface studies of the Fe{sub 82}Al{sub 18} alloy prepared from high purity Fe and Al by arc melting. The results summarize observations of the surface sensitive methods – high resolution scanning electron microscopy (HRSEM), slow energy electron microscopy (SLEEM), magneto-optical Kerr effect (MOKE), and conversion electron Mössbauer spectrometry (CEMS). Morphology of grains and grain boundaries obtained by HRSEM is observed in more detail by SLEEM. The CEMS results analyzed using free components with characteristic hyperfine parameters and by theoretical model, give evidence for A2 order of the as-prepared and as-quenched Fe{sub 82}Al{sub 18} sample surfaces. A small contribution of the oxide layer influences the shape of hysteresis loops and domain structure of the sample surface above all in the as-quenched state.

  18. Observation of Fermi-Pasta-Ulam Recurrence Induced by Breather Solitons in an Optical Microresonator

    Science.gov (United States)

    Bao, Chengying; Jaramillo-Villegas, Jose A.; Xuan, Yi; Leaird, Daniel E.; Qi, Minghao; Weiner, Andrew M.

    2016-10-01

    We present, experimentally and numerically, the observation of Fermi-Pasta-Ulam recurrence induced by breather solitons in a high-Q SiN microresonator. Breather solitons can be excited by increasing the pump power at a relatively small pump phase detuning in microresonators. Out of phase power evolution is observed for groups of comb lines around the center of the spectrum compared to groups of lines in the spectral wings. The evolution of the power spectrum is not symmetric with respect to the spectrum center. Numerical simulations based on the generalized Lugiato-Lefever equation are in good agreement with the experimental results and unveil the role of stimulated Raman scattering in the symmetry breaking of the power spectrum evolution. Our results show that optical microresonators can be exploited as a powerful platform for the exploration of soliton dynamics.

  19. Observation of Fermi-Pasta-Ulam Recurrence in an On-Chip Optical Microresonator

    CERN Document Server

    Bao, Chengying; Xuan, Yi; Leaird, Daniel E; Qi, Minghao; Weiner, Andrew M

    2016-01-01

    We present, experimentally and numerically, the observation of Fermi-Pasta-Ulam recurrence induced by breather solitons in a high-Q SiN microresonator. Breather solitons can be excited by increasing the pump power at a relatively small pump phase detuning in microresonators. Out of phase power evolution is observed for groups of comb lines around the center of the spectrum compared to groups of lines in the spectral wings. The evolution of the power spectrum is not symmetric with respect to the spectrum center. Numerical simulations based on the generalized Lugiato-Lefever equation are in good agreement with the experimental results and unveil the role of stimulated Raman scattering in the symmetry breaking of the power spectrum evolution. Our results shows that optical microresonators can be exploited as a powerful platform for the exploration of soliton dynamics.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chu, W. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather; Univ. of Chinese Academy of Sciences, Beijing (China). College of Earth Sciences; Qin, G. [Chinese Academy of Sciences, Beijing (China). State Key Lab. of Space Weather

    2016-04-01

    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. International Geomagnetic Reference Field: the seventh generation.

    Science.gov (United States)

    Barton, C. E.

    A seventh-generation revision of the International Geomagnetic Reference Field (IGRF) was adopted by the International Association of Geomagnetism and Aeronomy (IAGA) at the XXI General Assembly of the International Union of Geodesy and Geophysics in July 1995. The new spherical harmonic models adopted are based on weighted averages of candidate models submitted by NASA's Goddard Space Flight Center, the Russian Institute of Terrestrial Magnetism, Ionospheric, and Radio Wave Propagation - IZMIRAN, and jointly by the US Naval Oceanographic Office and the British Geological Survey. The revised IGRF specifies the Earth's main field from 1900 to 2000 and is declared to be definitive from 1945 to 1990. This paper lists the IGRF coefficients, describes the derivation of the new IGRF models, and examines aspects of the IGRF's accuracy, continuity, and behaviour during the 20th century.

  2. Trapping of strangelets in the geomagnetic field

    CERN Document Server

    Paulucci, L; Medina-Tanco, G A

    2007-01-01

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

  3. Optical and Ultraviolet Observations of the Very Young Type IIP SN 2014cx in NGC 337

    Science.gov (United States)

    Huang, Fang; Wang, Xiaofeng; Zampieri, Luca; Pumo, Maria Letizia; Arcavi, Iair; Brown, Peter J.; Graham, Melissa L.; Filippenko, Alexei V.; Zheng, WeiKang; Hosseinzadeh, Griffin; Howell, D. Andrew; McCully, Curtis; Rui, Liming; Valenti, Stefano; Zhang, Tianmeng; Zhang, Jujia; Zhang, Kaicheng; Wang, Lifan

    2016-12-01

    Extensive photometric and spectroscopic observations are presented for SN 2014cx, a Type IIP supernova (SN) exploding in the nearby galaxy NGC 337. The observations are performed in optical and ultraviolet bands, covering from -20 to +400 days from the peak light. The stringent detection limit from prediscovery images suggests that this supernova was actually detected within about one day after explosion. Evolution of the very early time light curve of SN 2014cx is similar to that predicted from a shock breakout and post-shock cooling decline before reaching the optical peak. Our photometric observations show that SN 2014cx has a plateau duration of ˜100 days, an absolute V-band magnitude of ˜ -16.5 mag at t≈ 50 days, and a nickel mass of 0.056 ± 0.008 {M}⊙ . The spectral evolution of SN 2014cx resembles that of normal SNe IIP like SN 1999em and SN 2004et, except that it has a slightly higher expansion velocity (˜4200 {km} {{{s}}}-1 at 50 days). From the cooling curve of photospheric temperature, we derive that the progenitor has a pre-explosion radius of ˜640 R {}⊙ , consistent with those obtained from SuperNova Explosion Code modeling (˜620 R {}⊙ ) and hydrodynamical modeling of the observables (˜570 R {}⊙ ). Moreover, the hydrodynamical simulations yield a total explosion energy of ˜ 0.4× {10}51 erg, and an ejected mass of ˜8 {M}⊙ . These results indicate that the immediate progenitor of SN 2014cx is likely a red supergiant star with a mass of ˜10 {M}⊙ .

  4. RHESSI/SAS Observations of the Optical Solar Limb Over More Than 14 Years

    Science.gov (United States)

    Fivian, Martin; Hudson, Hugh S.; Krucker, Sam

    2016-05-01

    The Solar Aspect System (SAS) of the RHESSI satellite measures the optical solar limb with a cadence typically set at 100 samples/s.RHESSI has observed the Sun continuously since its launch in early 2002, and we have acquired a unique data set ranging over more than a full 11-year solar cycle and consisting of about 4x10^10 single data points.The optics has a point spread of about 4.5 arcsec FWHM imaging the red continuum onto three linear CCD sensors with a pixel resolution of 1.7 arcsec.However, careful study of systematics, masking of contaminated data, and accumulation of data over appropriate time intervals has led to measurementswith sub-milli arcsec accuracy.Analyzing data for an initial period in 2004, these measurements have led to the most accurate oblateness measurement to date, 8.01+-0.14 milli arcsec (Fivian et al., 2008), a value consistent with models predicting an oblateness from surface rotation.An excess oblateness term can be attributed to magnetic elements possibly located in the enhanced network.We also study photometric properties of our data. Previous observations of latitude-dependent brightness variations at the limb had suggested the presence of a polar temperature excess as large as 1.5 K.The RHESSI observations, made with a rotating telescope in space, have great advantages in the rejection of systematic errors in the very precise photometry required for such an observation.Our measurements of latitude-dependent brightness variations at the limb lead to a quadrupolar term (a pole-to-equator temperature variation) of the order of 0.1 K, an order of magnitude smaller than previously reported.We present the analysis of these unique data, an overview of some results and we report on our progress as we apply our developed analysis method to the whole 14 years of data.

  5. X-ray/optical observations of A0535+26/HDE 245770 in quiescence

    CERN Document Server

    Orlandini, M; Campana, S; Del Sordo, S; De Martino, D; Frontera, F; Guarnieri, A; Israel, G; Masetti, N; Palazzi, E; Piccioni, A; Santangelo, A; Stella, L

    2004-01-01

    We present the result of three BeppoSAX observations of the X-ray binary pulsar A0535+26 in its quiescent state. The source is quite well detected up to 200 keV (6 sigma detection in the stronger observation). No Iron line is detected in the MECS data (3 sigma upper limit on its equivalent width of 150 eV). There is evidence of a soft excess below 2 keV. Pulsation is detected in all energy bands up to 10 keV, with a pulsed fraction of ~ 0.5, not varying with energy. There is a marginal detection (4 sigma) of a cyclotron resonance feature (CRF) at 118 +/- 20 keV in the PDS spectrum. During the BeppoSAX observations HDE 245770, the optical counterpart to A0535+26, was monitored spectroscopically and photometrically. These observations show that the Halpha and Hbeta lines previously observed in absorption returned in emission, indicating that the Be disk formed again. The presence of pulsation and a CRF is a clear indication that accretion onto the polar caps is occurring, and that the propeller mechanism is lea...

  6. Modeling the ocean effect of geomagnetic storms

    DEFF Research Database (Denmark)

    Olsen, Nils; Kuvshinov, A.

    2004-01-01

    At coastal sites, geomagnetic variations for periods shorter than a few days are strongly distorted by the conductivity of the nearby sea-water. This phenomena, known as the ocean (or coast) effect, is strongest in the magnetic vertical component. We demonstrate the ability to predict the ocean...... if the oceans are considered. Our analysis also indicates a significant local time asymmetry (i.e., contributions from spherical harmonics other than P-I(0)), especially during the main phase of the storm....

  7. MAGSAT for geomagnetic studies over Indian region

    Science.gov (United States)

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

    1981-01-01

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

  8. Radio-wave emission due to hypervelocity impacts and its correlation with optical observations

    Science.gov (United States)

    Takano, T.; Maki, K.; Yamori, A.

    This paper describes the most interesting phenomena of radio-wave emission due to hypervelocity impacts. A projectile of polycarbonate with 1.1 g weight was accelerated by a rail gun to 3.8 km/sec, and hit two targets which are a 2 mm thick aluminum plate upstream and a 45 mm diameter aluminum column downstream, respectively. The projectile first breaks wires to give a triggering signal to a data recorder, then penetrates the aluminum plate, and finally hit the column, The emitted radio-waves propagate through the chamber window, and are received by antennas at each frequency band. The receivers in 22 GHz- and 2 GHz-bands consist of a low noise amplifier, a mixer, a local oscillator and an IF amplifier , respectively. The receiver in 1 MHz-band is a simple RF amplifier. The outputs of all receivers are fed to a data recorder which is actually a high-speed digital oscilloscope with a large amount of memory. The radio-waves were successfully recorded in 22 GHz-band with 500 MHz bandwidth, in 2 GHz-band with 300 MHz bandwidth, and in 1MHz-band. The waveforms in 22 GHz- and 2 GHz-bands coincide well each other, and are composed of two groups of sharp impulses with a separation of about 20 micro seconds. The width of an impulse is less than 2 n sec. which is the resolution limit of the data recorder. We carried out optical observations using an ultra-high speed camera simultaneously through another window of the chamber. The time interval between scenes is 2 micro sec. We can see a faint light of the projectile before the first impact to the plate, and then a brilliant gas exploding backward from the plate and forward to the column. After hitting the column target, the brilliant gas flows to the chamber wall and is reflected back to make a mixture with dark gas in the chamber. Excellent correlation between radio-wave emission and the observed optical phenomena was obtained in the experiment. It is easily conceived that the radio-waves consist of quite a wide frequency

  9. Suzaku And Multi-Wavelength Observations of OJ 287 During the Periodic Optical Outburst in 2007

    Energy Technology Data Exchange (ETDEWEB)

    Seta, Hiromi; /Saitama U.; Isobe, N.; /Kyoto U.; Tashiro, Makoto S.; /Saitama U.; Yaji, Yuichi; /Saitama U.; Arai, Akira; /Hiroshima U.; Fukuhara, Masayuki; /Tokyo U. /Grad. U. for Adv. Stud., Nagano; Kohno, Kotaro; /Tokyo U.; Nakanishi, Koichiro; /Grad. U. for Adv. Stud., Nagano; Sasada, Mahito; /Hiroshima U.; Shimajiri, Yoshito; /Tokyo U. /Grad. U. for Adv. Stud., Nagano; Tosaki, Tomoka; /Grad. U. for Adv. Stud., Nagano; Uemura, Makoto; /Hiroshima U.; Anderhub, Hans; /Zurich, ETH; Antonelli, L.A.; /INFN, Rome; Antoranz, Pedro; /Madrid U.; Backes, Michael; /Dortmund U.; Baixeras, Carmen; /Barcelona, Autonoma U.; Balestra, Silvia; /Madrid U.; Barrio, Juan Abel; /Madrid U.; Bastieri, Denis; /Padua U. /INFN, Padua; Becerra Gonzalez, Josefa; /IAC, La Laguna /Dortmund U. /Lodz U. /Lodz U. /DESY /Zurich, ETH /Munich, Max Planck Inst. /Padua U. /INFN, Padua /Siena U. /INFN, Siena /Barcelona, IEEC /Munich, Max Planck Inst. /Barcelona, IEEC /Madrid U. /Zurich, ETH /Wurzburg U. /Zurich, ETH /Madrid U. /Munich, Max Planck Inst. /Zurich, ETH /Madrid U. /Barcelona, IFAE /IAC, La Laguna /Laguna U., Tenerife /INFN, Rome /Dortmund U. /Udine U. /INFN, Udine /INFN, Padua /Udine U. /INFN, Udine /Barcelona, IEEC /Madrid U. /Udine U. /INFN, Udine /Udine U. /INFN, Udine /Udine U. /INFN, Udine /IAC, La Laguna /Madrid, CIEMAT /Sierra Nevada Observ. /Zurich, ETH /Padua U. /INFN, Padua /Wurzburg U. /Barcelona, IFAE /UC, Davis /Barcelona, IFAE /Barcelona, IFAE /Madrid U. /Barcelona, Autonoma U. /Munich, Max Planck Inst. /IAC, La Laguna /Laguna U., Tenerife /Barcelona, IFAE /IAC, La Laguna /Munich, Max Planck Inst. /Barcelona, Autonoma U. /Munich, Max Planck Inst. /SLAC /IAC, La Laguna /Laguna U., Tenerife /Zurich, ETH /Wurzburg U. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Zurich, ETH /INFN, Rome /UC, Davis /Siena U. /INFN, Siena /Turku U. /Padua U. /INFN, Padua /Udine U. /INFN, Udine /Padua U. /INFN, Padua /Zurich, ETH /Munich, Max Planck Inst. /DESY /Sofiya, Inst. Nucl. Res. /Udine U. /INFN, Udine /Wurzburg U. /INFN, Rome /Padua U. /INFN, Padua /Barcelona, IFAE /Barcelona, IFAE /Siena U. /INFN, Siena /Wurzburg U. /Madrid U. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Barcelona, IEEC /Sierra Nevada Observ. /Barcelona, IFAE /Madrid U. /Turku U. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /UC, Santa Cruz /Madrid U. /Siena U. /INFN, Siena /Barcelona, IEEC /Turku U. /Padua U. /INFN, Padua /Zurich, ETH /Siena U. /INFN, Siena /Sierra Nevada Observ. /Udine U. /INFN, Udine /INFN, Trieste /Padua U. /INFN, Padua /Sierra Nevada Observ. /Padua U. /INFN, Padua /Barcelona, IFAE /Barcelona, IFAE /Dortmund U. /Barcelona, IEEC /ICREA, Barcelona /Barcelona, IFAE /Zurich, ETH /Barcelona, Autonoma U. /Wurzburg U. /Padua U. /INFN, Padua /Munich, Max Planck Inst. /INFN, Rome /Sierra Nevada Observ. /DESY /Padua U. /INFN, Padua /Udine U. /INFN, Udine /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Pisa U. /INFN, Pisa /Barcelona, IFAE /Barcelona, IEEC /Turku U. /Munich, Max Planck Inst. /Lodz U. /Lodz U. /Wurzburg U. /Siena U. /INFN, Siena /Zurich, ETH /Turku U. /INFN, Rome /Sofiya, Inst. Nucl. Res. /Barcelona, IFAE /Munich, Max Planck Inst. /DESY /ICREA, Barcelona /Barcelona, IEEC /Siena U. /INFN, Siena /Sofiya, Inst. Nucl. Res. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Barcelona, IEEC /Sierra Nevada Observ. /Barcelona, IFAE /Barcelona, Autonoma U.

    2011-12-01

    Suzaku observations of the blazar OJ 287 were performed in 2007 April 10-13 and November 7-9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be {Lambda} = 1.65 {+-} 0.02 and S{sub 1keV} = 215 {+-} 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum ({Lambda} = 1.50 {+-} 0.01) with a nearly doubled X-ray flux density S{sub 1keV} = 404{sub -5}{sup +6} nJy. Moreover, significant hard X-ray signals were detected up to {approx} 27 keV. In cooperation with the Suzaku, simultaneous radio, optical, and very-high-energy {gamma}-ray observations of OJ 287 were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 {+-} 0.46 Jy and 8.93 {+-} 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found to be higher by a factor of 2-3 than those in the quiescent state (1.73 {+-} 0.26 Jy and 3.03 {+-} 0.01 mJy at 86.75 Hz and in the V-band, respectively). No notable {gamma}-ray events were detected in either observation. The spectral energy distribution of OJ 287 indicated that the X-ray spectrum was dominated by inverse Compton radiation in both observations, while synchrotron radiation exhibited a spectral cutoff around the optical frequency. Furthermore, no significant difference in the synchrotron cutoff frequency was found between the quiescent and flaring states. According to a simple synchrotron self-Compton model, the change of the spectral energy distribution is due to an increase in the energy density of electrons with small changes of both the magnetic field strength and the maximum Lorentz factor of electrons.

  10. Geomagnetic effects on the average surface temperature

    Science.gov (United States)

    Ballatore, P.

    Several results have previously shown as the solar activity can be related to the cloudiness and the surface solar radiation intensity (Svensmark and Friis-Christensen, J. Atmos. Sol. Terr. Phys., 59, 1225, 1997; Veretenenkoand Pudovkin, J. Atmos. Sol. Terr. Phys., 61, 521, 1999). Here, the possible relationships between the averaged surface temperature and the solar wind parameters or geomagnetic activity indices are investigated. The temperature data used are the monthly SST maps (generated at RAL and available from the related ESRIN/ESA database) that represent the averaged surface temperature with a spatial resolution of 0.5°x0.5° and cover the entire globe. The interplanetary data and the geomagnetic data are from the USA National Space Science Data Center. The time interval considered is 1995-2000. Specifically, possible associations and/or correlations of the average temperature with the interplanetary magnetic field Bz component and with the Kp index are considered and differentiated taking into account separate geographic and geomagnetic planetary regions.

  11. Kristian Birkeland's pioneering investigations of geomagnetic disturbances

    Directory of Open Access Journals (Sweden)

    W. J. Burke

    2010-04-01

    Full Text Available 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

  12. Going for distance and going for speed: effort and optical variables shape information for distance perception from observation to response.

    Science.gov (United States)

    Hajnal, Alen; Bunch, David A; Kelty-Stephen, Damian G

    2014-05-01

    Visually guided distance perception reflects a relationship of geometrical optical variables with the effort required when traversing the distance. We probed how the representations encoding optical variables might define this relationship. Participants visually judged distances on sloped surfaces and reproduced these distances over flat terrain by walking while blindfolded. We examined the responses for the effects of optical variables (i.e., angular declinations from eye height) and tested whether four measures of trial-by-trial effort moderated the use of the represented optical variables. We predicted that observation time and response speed relative to the observed distance would accentuate the effects of encoded optical variables, and that response time and response speed relative to the traversed distance would reduce the effects of those variables. The results confirmed all of the effects except those of observation time. Given the benefits of longer study for strengthening a memory trace, the failure of observation time to predict the use of optical variables raises questions about the representational encoding of visual traces for distance perception. Relationships among optical variables and other effort measures implicate the interaction of processes across multiple time scales, as in cascade dynamics. Cascade dynamics may provide new directions for accounts of visually guided distance perception.

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

    Science.gov (United States)

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

    2017-02-01

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

  14. Geomagnetic Earthquake Precursors Improvement Formulation on the basis of SKO (Skopje) and PAG (Intermagnet) Geomagnetic Data

    CERN Document Server

    Mavrodiev, Strachimir Chterev

    2012-01-01

    In this paper we show that the simple analysis of the local geomagnetic field behaviour can serve as reliable imminent precursor for regional seismic activity increasing. As the first step the problem was investigated using one- component Dubna fluxgate magnetometer. The result of 2001-2004 Sofia monitoring confirmed many old papers for connection between Earth tide (Sun- Moon tides as earthquakes trigger) and jump (Geomagnetic quake) of daily averaged one minute standart deviation of the geomagnetic field. The second step (2004-present), which included analisys of three-component Danish fluxgate magnetometer data, worked in Skopje Seismological observatory, confirmed the first step result. The analysis of INTERMAGNET data stations around which was happened stronger earthquakes also confirmed our result. The distribution of time difference between the times of such earthquakes and local daily averaged tide vector movement for impending tide extreme confirms our estimate that the increasing seismicity is reali...

  15. Comparing simulated PSC optical properties with CALIPSO observations during the 2010 Antarctic winter

    Science.gov (United States)

    Zhu, Yunqian; Toon, Owen B.; Pitts, Michael C.; Lambert, Alyn; Bardeen, Charles; Kinnison, Douglas E.

    2017-01-01

    We simulate polar stratospheric clouds (PSCs) during the Antarctic winter of 2010 using the Specified Dynamics version of the Whole Atmosphere Community Climate Model/Community Aerosol and Radiation Model for Atmospheres (SD-WACCM/CARMA) model. The current PSC model contains microphysical schemes for supercooled ternary solutions (STS) and nitric acid trihydrate (NAT) particles, as well as a prognostic treatment for PSC ice particles and dehydration. Our simulations and CALIPSO satellite data suggest two major NAT particle formation mechanisms. The first mechanism is the nucleation of NAT from STS. Our model, with homogeneous nucleation rates of NAT from STS constrained by observations from the Arctic winter of 2010-2011, reproduces optical properties observed by CALIPSO over Antarctica in May and the timing of denitrification observed by the Microwave Limb Sounder within their uncertainties. On the other hand, the CALIPSO data indicate that our simulations are missing clouds containing small NAT particles with large number densities. We suggest these particles are most likely to form from ice clouds or STS in gravity waves, as found by previous investigations. The simulated cloud coverage agrees with the CALIPSO cloud coverage within a few percent on average with a correlation coefficient of 0.83. However, using the CALIPSO classification algorithm, simulated ice clouds often fall into Mix categories under the denitrified and dehydrated conditions. The model needs an improved ice microphysical representation, not only to allow ice particles to be a source of NAT but also to provide information on ice cloud particle number and size so that ice cloud optical properties can be more precisely calculated for comparison with CALIPSO data.

  16. Geomagnetic excursions date early hominid migration to China

    Science.gov (United States)

    Bhattacharya, Atreyee

    2012-09-01

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

  17. Optical observations of the type Ic supernova 2007gr in NGC 1058

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Juncheng; Wang, Xiaofeng; Li, Junzheng [Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing 100084 (China); Ganeshalingam, Mohan; Silverman, Jeffrey M.; Filippenko, Alexei V.; Li, Weidong; Chornock, Ryan; Steele, Thea, E-mail: cjc09@mails.tsinghua.edu.cn, E-mail: wang_xf@mail.tsinghua.edu.cn [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)

    2014-08-01

    We present extensive optical observations of the normal Type Ic supernova (SN) 2007gr, spanning from about one week before maximum light to more than one year thereafter. The optical light and color curves of SN 2007gr are very similar to those of the broad-lined Type Ic SN 2002ap, but the spectra show remarkable differences. The optical spectra of SN 2007gr are characterized by unusually narrow lines, prominent carbon lines, and slow evolution of the line velocity after maximum light. The earliest spectrum (taken at t = –8 days) shows a possible signature of helium (He I λ5876 at a velocity of ∼19,000 km s{sup –1}). Moreover, the larger intensity ratio of the [O I] λ6300 and λ6364 lines inferred from the early nebular spectra implies a lower opacity of the ejecta shortly after the explosion. These results indicate that SN 2007gr perhaps underwent a less energetic explosion of a smaller-mass Wolf-Rayet star (∼8-9 M{sub ☉}) in a binary system, as favored by an analysis of the progenitor environment through pre-explosion and post-explosion Hubble Space Telescope images. In the nebular spectra, asymmetric double-peaked profiles can be seen in the [O I] λ6300 and Mg I] λ4571 lines. We suggest that the two peaks are contributed by the blueshifted and rest-frame components. The similarity in velocity structure and the different evolution of the strength of the two components favor an aspherical explosion with the ejecta distributed in a torus or disk-like geometry, but inside the ejecta the O and Mg have different distributions.

  18. Observationally-constrained estimates of aerosol optical depths (AODs) over East Asia via data assimilation techniques

    Science.gov (United States)

    Lee, K.; Lee, S.; Song, C. H.

    2015-12-01

    Not only aerosol's direct effect on climate by scattering and absorbing the incident solar radiation, but also they indirectly perturbs the radiation budget by influencing microphysics and dynamics of clouds. Aerosols also have a significant adverse impact on human health. With an importance of aerosols in climate, considerable research efforts have been made to quantify the amount of aerosols in the form of the aerosol optical depth (AOD). AOD is provided with ground-based aerosol networks such as the Aerosol Robotic NETwork (AERONET), and is derived from satellite measurements. However, these observational datasets have a limited areal and temporal coverage. To compensate for the data gaps, there have been several studies to provide AOD without data gaps by assimilating observational data and model outputs. In this study, AODs over East Asia simulated with the Community Multi-scale Air Quality (CMAQ) model and derived from the Geostationary Ocean Color Imager (GOCI) observation are interpolated via different data assimilation (DA) techniques such as Cressman's method, Optimal Interpolation (OI), and Kriging for the period of the Distributed Regional Aerosol Gridded Observation Networks (DRAGON) Campaign (March - May 2012). Here, the interpolated results using the three DA techniques are validated intensively by comparing with AERONET AODs to examine the optimal DA method providing the most reliable AODs over East Asia.

  19. Subaru Telescope adaptive optics observations of gravitationally lensed quasars in the Sloan Digital Sky Survey

    Science.gov (United States)

    Rusu, Cristian E.; Oguri, Masamune; Minowa, Yosuke; Iye, Masanori; Inada, Naohisa; Oya, Shin; Kayo, Issha; Hayano, Yutaka; Hattori, Masayuki; Saito, Yoshihiko; Ito, Meguru; Pyo, Tae-Soo; Terada, Hiroshi; Takami, Hideki; Watanabe, Makoto

    2016-05-01

    We present the results of an imaging observation campaign conducted with the Subaru Telescope adaptive optics system (IRCS+AO188) on 28 gravitationally lensed quasars and candidates (23 doubles, 1 quad, 1 possible triple, and 3 candidates) from the SDSS Quasar Lens Search. We develop a novel modelling technique that fits analytical and hybrid point spread functions (PSFs), while simultaneously measuring the relative astrometry, photometry, as well as the lens galaxy morphology. We account for systematics by simulating the observed systems using separately observed PSF stars. The measured relative astrometry is comparable with that typically achieved with the Hubble Space Telescope, even after marginalizing over the PSF uncertainty. We model for the first time the quasar host galaxies in five systems, without a priori knowledge of the PSF, and show that their luminosities follow the known correlation with the mass of the supermassive black hole. For each system, we obtain mass models far more accurate than those previously published from low-resolution data, and we show that in our sample of lensing galaxies the observed light profile is more elliptical than the mass, for ellipticity ≳0.25. We also identify eight doubles for which the sources of external and internal shear are more reliably separated, and should therefore be prioritized in monitoring campaigns aimed at measuring time delays in order to infer the Hubble constant.

  20. Nine martian years of dust optical depth observations: A reference dataset

    Science.gov (United States)

    Montabone, Luca; Forget, Francois; Kleinboehl, Armin; Kass, David; Wilson, R. John; Millour, Ehouarn; Smith, Michael; Lewis, Stephen; Cantor, Bruce; Lemmon, Mark; Wolff, Michael

    2016-07-01

    We present a multi-annual reference dataset of the horizontal distribution of airborne dust from martian year 24 to 32 using observations of the martian atmosphere from April 1999 to June 2015 made by the Thermal Emission Spectrometer (TES) aboard Mars Global Surveyor, the Thermal Emission Imaging System (THEMIS) aboard Mars Odyssey, and the Mars Climate Sounder (MCS) aboard Mars Reconnaissance Orbiter (MRO). Our methodology to build the dataset works by gridding the available retrievals of column dust optical depth (CDOD) from TES and THEMIS nadir observations, as well as the estimates of this quantity from MCS limb observations. The resulting (irregularly) gridded maps (one per sol) were validated with independent observations of CDOD by PanCam cameras and Mini-TES spectrometers aboard the Mars Exploration Rovers "Spirit" and "Opportunity", by the Surface Stereo Imager aboard the Phoenix lander, and by the Compact Reconnaissance Imaging Spectrometer for Mars aboard MRO. Finally, regular maps of CDOD are produced by spatially interpolating the irregularly gridded maps using a kriging method. These latter maps are used as dust scenarios in the Mars Climate Database (MCD) version 5, and are useful in many modelling applications. The two datasets (daily irregularly gridded maps and regularly kriged maps) for the nine available martian years are publicly available as NetCDF files and can be downloaded from the MCD website at the URL: http://www-mars.lmd.jussieu.fr/mars/dust_climatology/index.html

  1. Reducing multisensor monthly mean aerosol optical depth uncertainty: 2. Optimal locations for potential ground observation deployments

    Science.gov (United States)

    Li, Jing; Li, Xichen; Carlson, Barbara E.; Kahn, Ralph A.; Lacis, Andrew A.; Dubovik, Oleg; Nakajima, Teruyuki

    2017-04-01

    Surface remote sensing of aerosol properties provides "ground truth" for satellite and model validation and is an important component of aerosol observation system. Due to the different characteristics of background aerosol variability, information obtained at different locations usually has different spatial representativeness, implying that the location should be carefully chosen so that its measurement could be extended to a greater area. In this study, we present an objective observation array design technique that automatically determines the optimal locations with the highest spatial representativeness based on the Ensemble Kalman Filter (EnKF) theory. The ensemble is constructed using aerosol optical depth (AOD) products from five satellite sensors. The optimal locations are solved sequentially by minimizing the total analysis error variance, which means that observations at these locations will reduce the background error variance to the largest extent. The location determined by the algorithm is further verified to have larger spatial representativeness than some other arbitrary location. In addition to the existing active Aerosol Robotic Network (AERONET) sites, the 40 selected optimal locations are mostly concentrated on regions with both high AOD inhomogeneity and its spatial representativeness, namely, the Sahel, South Africa, East Asia, and North Pacific Islands. These places should be the focuses of establishing future AERONET sites in order to further reduce the uncertainty in the monthly mean AOD. Observations at these locations contribute to approximately 50% of the total background uncertainty reduction.

  2. Optical Coherence Tomography Observation of Gonio Structures during Microhook Ab Interno Trabeculotomy

    Directory of Open Access Journals (Sweden)

    Masaki Tanito

    2017-01-01

    Full Text Available Introduction. Intraoperative observation of ocular structures using microscope-integrated optical coherence tomography (iOCT has been adopted recently. I report my initial feasibility assessment of iOCT for the incised trabecular meshwork observation during microhook ab interno trabeculotomy. Case Series. Both the nasal and temporal sides or either side of the trabecular meshwork/inner wall of Schlemm’s canal was incised more than 3 clock hours. After then, under observation using a Swan-Jacob gonioprism lens with the real-time 5-line scan mode, OCT images of the area were successfully acquired in 10 (83% of 12 sides in nine eyes. Based on the appearance of the acquired images of the 10 sides, the trabeculotomy cleft could be classified into three incisional patterns, that is, six (60% anterior-opening patterns (posterior-based flap, three (30% middle-opening patterns (posterior- and anterior-based flaps, and one (10% posterior-opening pattern (anterior-based flap, according to the predominant locations of the trabecular meshwork flaps. Conclusion. Intraoperative observation of the gonio structures including the trabeculotomy cleft was feasible using the RESCAN 700 in combination with a gonioprism.

  3. CALIPSO observations of wave-induced PSCs with near-unity optical depth over Antarctica in 2006-2007

    CERN Document Server

    Noel, Vincent; Chepfer, Hélène

    2009-01-01

    Ground-based and satellite observations have hinted at the existence of polar stratospheric clouds (PSCs) with relatively high optical depths, even if optical depth values are hard to come by. This study documents a type II PSC observed from spaceborne lidar, with visible optical depths up to 0.8. Comparisons with multiple temperature fields, including reanalyses and results from mesoscale simulations, suggest that intense small-scale temperature fluctuations due to gravity waves play an important role in its formation, while nearby observations show the presence of a potentially related type Ia PSC farther downstream inside the polar vortex. Following this first case, the geographic distribution and microphysical properties of PSCs with optical depths above 0.3 are explored over Antarctica during the 2006 and 2007 austral winters. These clouds are rare (less than 1% of profiles) and concentrated over areas where strong winds hit steep ground slopes in the Western Hemisphere, especially over the peninsula. Su...

  4. Radio Galaxy 3C 230 Observed with Gemini Laser-Adaptive-Optics Integral-Field Spectroscopy

    CERN Document Server

    Steinbring, Eric

    2011-01-01

    The Altair laser-guide-star adaptive optics facility combined with the Near-Infrared Integral Field Spectrometer (NIFS) on Gemini North have been employed to study the morphology and kinematics of 3C 230 at z=1.5, the first such observations of a high-redshift radio galaxy. These suggest a bi-polar outflow spanning 0"9 (~16 kpc projected distance for a standard lambda-CDM cosmology) reaching a mean relative velocity of 235 km/s in redshifted H-alpha + [NII] and [SII] emission. Structure is resolved to 0"1 (0.8 kpc), well correlated with optical images from the Hubble Space Telescope and Very Large Array radio maps obtained at similar spatial resolution. Line diagnostics suggest that over the 10^7 yr to 10^8 yr duration of its AGN activity, gas has been ejected into bright turbulent lobes at rates comparable to star formation, although constituting perhaps only 1 percent of the baryonic mass in the galaxy.

  5. Multi-band optical follow-up observations of GRB 020813 at KISO and Bisei observatories

    CERN Document Server

    Urata, Y; Miyata, T; Mito, H; Kawabata, T; Nakada, Y; Aoki, T; Soyano, T; Tarusawa, K; Yoshida, A; Tamagawa, T; Makishima, K

    2003-01-01

    Observations were made of the optical afterglow of GRB020813 (Fox, Blake & Price, 2002) with the KISO observatory 1.05 m Schmidt telescope and the Bisei astronomical observatory 1.01 m telescope. Four-band ($B, V, R$, and $I$) photometric data points were obtained from 2002, August 13 10:52 to 16:46 UT, or 0.346$-$0.516 days after the burst. In order to investigate the early-time ($<$1 day) evolution of the afterglow, four-band light curves were produced by analyzing the data taken at these two astronomical observatories, as well as publicly released data taken by the Magellan Baade telescope (Gladders and Hall, 2002c). The light curves can be approximated by a broken power law, of which the indices are approximately 0.46 and 1.33 before and after a break at $\\sim$0.2 days, respectively. The optical spectral index stayed approximately constant at $\\sim$0.9 over 0.17 $\\sim$ 4.07 days after the burst. Since the temporal decay index after the break and the spectral index measured at that time are both con...

  6. Optical and near-infrared observations of SN 2013dx associated with GRB 130702A

    CERN Document Server

    Toy, V L; Silverman, J M; Butler, N R; Cucchiara, A; Watson, A M; Bersier, D; Perley, D A; Margutti, R; Bellm, E; Bloom, J S; Cao, Y; Capone, J I; Clubb, K; Corsi, A; de Diego, J A; Filippenko, A V; Fox, O D; Gal-Yam, A; Gehrels, N; Georgiev, L; González, J J; Kasliwal, M M; Kelly, P L; Kulkarni, S R; Kutyrev, A S; Lee, W H; Prochaska, J X; Ramirez-Ruiz, E; Richer, M G; Román, C; Singer, L; Stern, D; Troja, E; Veilleux, S

    2015-01-01

    We present optical and near-infrared light curves and optical spectra of SN 2013dx, associated with the nearby (redshift 0.145) gamma-ray burst GRB 130702A. The prompt isotropic gamma-ray energy released from GRB 130702A is measured to be $E_{\\gamma,\\mathrm{iso}} = 6.4_{-1.0}^{+1.3} \\times 10^{50}$erg (1keV to 10MeV in the rest frame), placing it intermediate between low-luminosity GRBs like GRB 980425/SN 1998bw and the broader cosmological population. We compare the observed $g^{\\prime}r^{\\prime}i^{\\prime}z^{\\prime}$ light curves of SN 2013dx to a SN 1998bw template, finding that SN 2013dx evolves $\\sim20$% faster (steeper rise time), with a comparable peak luminosity. Spectroscopically, SN 2013dx resembles other broad-lined Type Ic supernovae, both associated with (SN 2006aj and SN 1998bw) and lacking (SN 1997ef, SN 2007I, and SN 2010ah) gamma-ray emission, with photospheric velocities around peak of $\\sim$21,000 km s$^{-1}$. We construct a quasi-bolometric ($g^{\\prime}r^{\\prime}i^{\\prime}z^{\\prime}yJH$) li...

  7. OISTER Optical and Near-Infrared Observations of Type Iax Supernova 2012Z

    CERN Document Server

    Yamanaka, Masayuki; Kawabata, Koji S; Tanaka, Masaomi; Tominaga, Nozomu; Akitaya, Hiroshi; Nagayama, Takahiro; Kuroda, Daisuke; Takahashi, Jun; Saito, Yoshihiko; Yanagisawa, Kenshi; Fukui, Akihiko; Miyanoshita, Ryo; Watanabe, Makoto; Arai, Akira; Isogai, Mizuki; Hattori, Takashi; Hanayama, Hidekazu; Itoh, Ryosuke; Ui, Takahiro; Takaki, Katsutoshi; Ueno, Issei; Yoshida, Michitoshi; Ali, Gamal B; Essam, Ahmed; Ozaki, Akihito; Nakao, Hikaru; Hamamoto, Ko; Nogami, Daisaku; Morokuma, Tomoki; Oasa, Yumiko; Izumiura, Hideyuki; Sekiguchi, Kazuhiro

    2015-01-01

    We report observations of the Type Iax supernova (SN Iax) 2012Z at optical and near-infrared wavelengths from immediately after the explosion until $\\sim$ $260$ days after the maximum luminosity using the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER) Target-of-Opportunity (ToO) program and the Subaru telescope. We found that the near-infrared (NIR) light curve evolutions and color evolutions are similar to those of SNe Iax 2005hk and 2008ha. The NIR absolute magnitudes ($M_{J}\\sim-18.1$ mag and $M_{H}\\sim-18.3$ mag) and the rate of decline of the light curve ($\\Delta$ $m_{15}$($B$)$=1.6 \\pm 0.1$ mag) are very similar to those of SN 2005hk ($M_{J}\\sim-17.7$ mag, $M_{H}\\sim$$-18.0$ mag, and $\\Delta$ $m_{15}$($B$)$\\sim1.6$ mag), yet differ significantly from SNe 2008ha and 2010ae ($M_{J}\\sim-14 - -15$ mag and $\\Delta$ $m_{15}$($B$)$\\sim2.4-2.7$ mag). The estimated rise time is $12.0 \\pm 3.0$ days, which is significantly shorter than that of SN 2005hk or any other Ia SNe. The rapi...

  8. Assessment of 10 Year Record of Aerosol Optical Depth from OMI UV Observations

    Science.gov (United States)

    Ahn, Changwoo; Torres, Omar; Jethva, Hiren

    2014-01-01

    The Ozone Monitoring Instrument (OMI) onboard the EOS-Aura satellite provides information on aerosol optical properties by making use of the large sensitivity to aerosol absorption in the near-ultraviolet (UV) spectral region. Another important advantage of using near UV observations for aerosol characterization is the low surface albedo of all terrestrial surfaces in this spectral region that reduces retrieval errors associated with land surface reflectance characterization. In spite of the 13 × 24 square kilometers coarse sensor footprint, the OMI near UV aerosol algorithm (OMAERUV) retrieves aerosol optical depth (AOD) and single-scattering albedo under cloud-free conditions from radiance measurements at 354 and 388 nanometers. We present validation results of OMI AOD against space and time collocated Aerosol Robotic Network measured AOD values over multiple stations representing major aerosol episodes and regimes. OMAERUV's performance is also evaluated with respect to those of the Aqua-MODIS Deep Blue and Terra-MISR AOD algorithms over arid and semi-arid regions in Northern Africa. The outcome of the evaluation analysis indicates that in spite of the "row anomaly" problem, affecting the sensor since mid-2007, the long-term aerosol record shows remarkable sensor stability.

  9. Optical observations of PSR J2021+3651 in the Dragonfly Nebula with the GTC

    CERN Document Server

    Kirichenko, Aida; Shternin, Peter; Shibanov, Yuriy; Ryspaeva, Elizaveta; Zyuzin, Dima; Durant, Martin; Kargaltsev, Oleg; Pavlov, George; Cabrera-Lavers, Antonio

    2015-01-01

    PSR J2021+3651 is a 17 kyr old rotation powered pulsar detected in the radio, X-rays, and $\\gamma$-rays. It powers a torus-like pulsar wind nebula with jets, dubbed the Dragonfly, which is very similar to that of the Vela pulsar. The Dragonfly is likely associated with the extended TeV source VER J2019+368 and extended radio emission. We conducted first deep optical observations with the GTC in the Sloan $r'$ band to search for optical counterparts of the pulsar and its nebula. No counterparts were detected down to $r'\\gtrsim27.2$ and $\\gtrsim24.8$ for the point-like pulsar and the compact X-ray nebula, respectively. We also reanalyzed Chandra archival X-ray data taking into account an interstellar extinction--distance relation, constructed by us for the Dragonfly line of sight using the red-clump stars as standard candles. This allowed us to constrain the distance to the pulsar, $D=1.8^{+1.7}_{-1.4}$ kpc at 90% confidence. It is much smaller than the dispersion measure distance of $\\sim$12 kpc but compatible...

  10. Capability of Cherenkov Telescopes to Observe Ultra-fast Optical Flares

    CERN Document Server

    Deil, C; Hermann, G; Clapson, A -C; Förster, A; Van Eldik, C; Hofmann, W

    2008-01-01

    The large optical reflector (~ 100 m^2) of a H.E.S.S. Cherenkov telescope was used to search for very fast optical transients of astrophysical origin. 43 hours of observations targeting stellar-mass black holes and neutron stars were obtained using a dedicated photometer with microsecond time resolution. The photometer consists of seven photomultiplier tube pixels: a central one to monitor the target and a surrounding ring of six pixels to veto background events. The light curves of all pixels were recorded continuously and were searched offline with a matched-filtering technique for flares with a duration of 2 us to 100 ms. As expected, many unresolved (500 us) background events originating in the earth's atmosphere were detected. In the time range 3 to 500 us the measurement is essentially background-free, with only eight events detected in 43 h; five from lightning and three presumably from a piece of space debris. The detection of flashes of brightness ~ 0.1 Jy and only 20 us duration from the space debri...

  11. The effect of the high-speed stream following the corotating interaction region on the geomagnetic activities

    Directory of Open Access Journals (Sweden)

    S. Watari

    Full Text Available The high-speed stream following the corotating interaction regions (CIRs was analyzed. As a result of the analysis, it is found that the geomagnetic field is continuously disturbed in the high-speed stream in question. The geomagnetic disturbances with long duration recurred several rotations between December 1993 and June 1994. These disturbances were associated with a large recurrent coronal hole expanding from the south pole of the Sun. High-speed solar wind from this coronal hole was observed by the IMP-8 satellite during this period. However, the observed intensities of the geomagnetic disturbances were different for each recurrent period. This is explained by the seasonal effect. The disturbed geomagnetic condition continued in the high-speed stream after the passage of the CIRs. The long duration of these disturbances can be explained by the continuous energy input into the Earth's magnetosphere from the high-speed regions following the CIRs. This kind of long-duration geomagnetic disturbance in association with coronal holes has been observed in the declining phase of other solar cycles. The relation between the coronal-hole area and the maximum solar-wind velocity is not good for the well-developed large coronal hole analyzed here.

  12. Apices of maxillary premolars observed by swept source optical coherence tomography

    Science.gov (United States)

    Ebihara, Arata; Iino, Yoshiko; Yoshioka, Toshihiko; Hanada, Takahiro; Sunakawa, Mitsuhiro; Sumi, Yasunori; Suda, Hideaki

    2015-02-01

    Apicoectomy is performed for the management of apical periodontitis when orthograde root canal treatment is not possible or is ineffective. Prior to the surgery, cone beam computed tomography (CBCT) examination is often performed to evaluate the lesion and the adjacent tissues. During the surgical procedure, the root apex is resected and the resected surface is usually observed under dental operating microscope (DOM). However, it is difficult to evaluate the details and the subsurface structure of the root using CBCT and DOM. A new diagnostic system, swept source optical coherence tomography (SS-OCT), has been developed to observe the subsurface anatomical structure. The aim of this study was to observe resected apical root canals of human maxillary premolars using SS-OCT and compare the findings with those observed using CBCT and DOM. Six extracted human maxillary premolars were used. After microfocus computed tomography (Micro CT; for gold standard) and CBCT scanning of the root, 1 mm of the apex was cut perpendicular to the long axis of the tooth. Each resected surface was treated with EDTA, irrigated with saline solution, and stained with methylene blue dye. The resected surface was observed with DOM and SS-OCT. This sequence was repeated three times. The number of root canals was counted and statistically evaluated. There was no significant difference in the accuracy of detecting root canals among CBCT, DOM and SS-OCT (p > 0.05, Wilcoxon test). Because SS-OCT can be used in real time during surgery, it would be a useful tool for observing resected apical root canals.

  13. Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2012-01-01

    Full Text Available This study estimates the emission fluxes of a range of aerosol species and aerosol precursor at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The performance of the assimilation is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. The assimilation is more efficient over land than over ocean. The impact of the assimilation of fine mode AOD over ocean demonstrates potential for further improvement by including fine mode AOD observations over continents. The Angström exponent is also improved in African, European and dusty stations. The estimated emission flux for black carbon is 14.5 Tg yr−1, 119 Tg yr−1 for organic matter, 17 Pg yr−1 for sea salt, 82.7 TgS yr−1 for SO2 and 1383 Tg yr−1 for desert dust. They represent a difference of +45%, +40%, +26%, +13% and −39% respectively, with respect to the a priori values. The initial errors attributed to the emission fluxes are reduced for all estimated species.

  14. Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2012-05-01

    Full Text Available This study estimates the emission fluxes of a range of aerosol species and one aerosol precursor at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The performance of the assimilation is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. These improvements are larger over land than over ocean. The impact of the assimilation of fine mode AOD over ocean demonstrates potential for further improvement by including fine mode AOD observations over continents. The Angström exponent is also improved in African, European and dusty stations. The estimated emission flux for black carbon is 15 Tg yr−1, 119 Tg yr−1 for particulate organic matter, 17 Pg yr−1 for sea salt, 83 TgS yr−1 for SO2 and 1383 Tg yr−1 for desert dust. They represent a difference of +45 %, +40 %, +26 %, +13 % and −39 % respectively, with respect to the a priori values. The initial errors attributed to the emission fluxes are reduced for all estimated species.

  15. Follow-Up Discovery Channel Telescope Observations of Transients and Variables from Optical Time Domain Surveys

    Science.gov (United States)

    Gezari, Suvi; Liu, Tingting; Hung, Tiara

    2017-01-01

    We highlight the capabilities of the Discovery Channel Telescope (DCT) for follow-up observations of transients and variables discovered by optical time-domain surveys. We present two DCT programs: 1) extended-baseline imaging with the Large Monolithic Imager of periodically variable quasars from the Pan-STARRS1 survey to identify binary supermassive black hole candidates, and 2) spectroscopic classification with the DeVeny spectrograph of nuclear transients from the iPTF survey to identify tidal disruption event candidates. We demonstrate that DCT is well-matched to the magnitude ranges of the transients and variables discovered by these surveys, and has played an important role in their classification and characterization.

  16. Anomalous Fiber Optic Gyroscope Signals Observed above Spinning Rings at Low Temperature

    CERN Document Server

    Tajmar, M; Seifert, B

    2008-01-01

    Precision fiber optic gyroscopes were mounted mechanically de-coupled above spinning rings inside a cryostat. Below a critical temperature (typically <30 K), the gyroscopes measure a significant deviation from their usual Earth rotation offset proportional to the applied angular ring velocity with maximum signals towards lower temperatures. The anomalous gyroscope signal is about 8 orders of magnitude smaller then the applied angular ring velocity, compensating about one third of the Earth rotation offset at an angular top speed of 420 rad/s. Moreover, our data shows a parity violation as the effect appears to be dominant for rotation against the Earth's spin. No systematic effect was found to explain this effect including the magnetic environment, vibration and helium gas friction suggesting that our observation is a new low temperature phenomenon. Tests in various configurations suggest that the anomalous signals is originating from the rotating helium in our facilities.

  17. Observation of Optical Undular Bores in Multiple Four-Wave Mixing

    Directory of Open Access Journals (Sweden)

    J. Fatome

    2014-05-01

    Full Text Available We demonstrate that wave-breaking dramatically affects the dynamics of nonlinear frequency conversion processes that operate in the regime of high efficiency (strong multiple four-wave mixing. In particular, by exploiting an all-optical-fiber platform, we show that input modulations propagating in standard telecom fibers in the regime of weak normal dispersion lead to the formation of undular bores (dispersive shock waves that mimic the typical behavior of dispersive hydrodynamics exhibited, e.g., by gravity waves and tidal bores. Thanks to the nonpulsed nature of the beat signal employed in our experiment, we are able to clearly observe how the periodic nature of the input modulation forces adjacent undular bores to collide elastically.

  18. XMM-Newton and Optical Observations of Cataclysmic Variables from the Sloan Digital Sky Survey

    Science.gov (United States)

    Hilton, Eric J.; Szkody, Paula; Mukadam, Anjum; Henden, Arne; Dillon, William; Schmidt, Gary D.

    2009-03-01

    We report on XMM-Newton and optical results for six cataclysmic variables that were selected from Sloan Digital Sky Survey (SDSS) spectra because they showed strong He II emission lines, indicative of being candidates for containing white dwarfs with strong magnetic fields. While high X-ray background rates prevented optimum results, we are able to confirm SDSS J233325.92+152222.1 as an intermediate polar from its strong pulse signature at 21 minutes and its obscured hard X-ray spectrum. Ground-based circular polarization and photometric observations were also able to confirm SDSS J142256.31 - 022108.1 as a polar with a period near 4 hr. Photometry of SDSS J083751.00+383012.5 and SDSS J093214.82+495054.7 solidifies the orbital period of the former as 3.18 hr and confirms the latter as a high-inclination system with deep eclipses.

  19. Observation of Optical Undular Bores in Multiple Four-Wave Mixing

    Science.gov (United States)

    Fatome, J.; Finot, C.; Millot, G.; Armaroli, A.; Trillo, S.

    2014-04-01

    We demonstrate that wave-breaking dramatically affects the dynamics of nonlinear frequency conversion processes that operate in the regime of high efficiency (strong multiple four-wave mixing). In particular, by exploiting an all-optical-fiber platform, we show that input modulations propagating in standard telecom fibers in the regime of weak normal dispersion lead to the formation of undular bores (dispersive shock waves) that mimic the typical behavior of dispersive hydrodynamics exhibited, e.g., by gravity waves and tidal bores. Thanks to the nonpulsed nature of the beat signal employed in our experiment, we are able to clearly observe how the periodic nature of the input modulation forces adjacent undular bores to collide elastically.

  20. Optical Afterglow Observations of the Unusual Short-Duration Gamma-Ray Burst 040924

    CERN Document Server

    Huang, K Y; Filippenko, A V; Hu, J H; Ip, W H; Kuo, P H; Li, W; Lin, H C; Lin, Z Y; Makishima, K; Onda, K; Qiu, Y; Tamagawa, T

    2005-01-01

    The 1-m telescope at Lulin Observatory and the 0.76-m Katzman Automatic Imaging Telescope at Lick Observatory were used to observe the optical afterglow of the short-duration (1.2--1.5 s) gamma-ray burst (GRB) 040924. This object has a soft high-energy spectrum, thus making it an exceptional case, perhaps actually belonging to the short-duration tail of the long-duration GRBs. Our data, combined with other reported measurements, show that the early R-band light curve can be described by two power laws with index alpha = -0.7 (at t = 16-50 min) and alpha = -1.06 (at later times). The rather small difference in the spectral indices can be more easily explained by an afterglow model invoking a cooling break rather than a jet break.