1,843 research outputs found

    Short term Variability of the Sun Earth System: An Overview of Progress Made during the CAWSES II Period

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    This paper presents an overview of results obtained during the CAWSES II period on the short term variability of the Sun and how it affects the near Earth space environment. CAWSES II was planned to examine the behavior of the solar terrestrial system as the solar activity climbed to its maximum phase in solar cycle 24. After a deep minimum following cycle 23, the Sun climbed to a very weak maximum in terms of the sunspot number in cycle 24 (MiniMax24), so many of the results presented here refer to this weak activity in comparison with cycle 23. The short term variability that has immediate consequence to Earth and geospace manifests as solar eruptions from closed field regions and high speed streams from coronal holes. Both electromagnetic (flares) and mass emissions (coronal mass ejections, CMEs) are involved in solar eruptions, while coronal holes result in high speed streams that collide with slow wind forming the so called corotating interaction regions (CIRs). Fast CMEs affect Earth via leading shocks accelerating energetic particles and creating large geomagnetic storms. CIRs and their trailing high speed streams (HSSs), on the other hand, are responsible for recurrent small geomagnetic storms and extended (days) of auroral zone activity, respectively. The latter lead to the acceleration of relativistic magnetospheric killer electrons. One of the major consequences of the weak solar activity is the altered physical state of the heliosphere that has serious implications for the shock-driving and storm causing properties of CMEs. Finally, a discussion is presented on extreme space weather events prompted by the 2012 July 23 super storm event that occurred on the backside of the Sun. Many of these studies were enabled by the simultaneous availability of remote-sensing and in situ observations from multiple vantage points with respect to the Sun Earth line.Comment: 85 pages, 30 figures, 2 tables, Accepted for publication in Progress in Earth and Planetary Science on April 13, 201

    Real-time ISEE data system

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    A real-time ISEE data system directed toward predicting geomagnetic substorms and storms is discussed. Such a system may allow up to 60+ minutes advance warning of magnetospheric substorms and up to 30 minute warnings of geomagnetic storms (and other disturbances) induced by high-speed streams and solar flares. The proposed system utilizes existing capabilities of several agencies (NASA, NOAA, USAF), and thereby minimizes costs. This same concept may be applicable to data from other spacecraft, and other NASA centers; thus, each individual experimenter can receive quick-look data in real time at his or her base institution

    Criteria of interplanetary parameters causing intense magnetic storms (Dst less than -100nT)

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    Ten intense storms occurred during the 500 days of August 16, 1978 to December 28, 1979. From the analysis of ISEE-3 field and plasma data, it is found that the interplanetary cause of these storms are long-duration, large and negative IMF B sub Z events, associated with interplanetary duskward-electric fields greater than 5 mV/m. Because a one-to-one relationship was found between these interplanetary events and intense storms, it is suggested that these criteria can, in the future, be used as predictors of intense storms by an interplanetary monitor such as ISEE-3. These B sub Z events are found to occur in association with large amplitudes of the IMF magnitude within two days after the onset of either high-speed solar wind streams or of solar wind density enhancement events, giving important clues to their interplanetary origin. Some obvious possibilities will be discussed. The close proximity of B sub Z events and magnetic storms to the onset of high speed streams or density enhancement events is in sharp contrast to interplanetary Alfven waves and HILDCAA events previously reported, and thus the two interplanetary features corresponding geomagnetic responses can be thought of as being complementary in nature. An examination of opposite polarity B sub Z events with the same criteria show that their occurrence is similar both in number as well as in their relationship to interplanetary disturbances, and that they lead to low levels of geomagnetic activity

    Developing a new English language program

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    Kapi‘olani Community College (KCC) has been offering a successful English as a Second Language (ESL) Program for many years. The college, however, does not offer an English language program designed for second language learners who are not academically-motivated. Should KCC develop such a non-academic English language program? Would it serve KCC’s mission, goals, and objectives? Another important question to ask is if there is enough market demand to support the program, and if so, what kind of program would meet the needs of the potential program participants? The purpose of this study is to try to answer these questions

    Energetic particles of the outer regions of planetary magnetospheres

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    High energy particles, with energies above those attainable by adiabatic or steady-state electric field acceleration, have been observed in and around the outer regions of planetary magnetospheres. Acceleration by large amplitude sporadic cross-tail electric fields over an order of magnitude greater than steady-state convection fields is proposed as a source of these particles. It is suggested that such explosive electric fields will occur intermittently in the vicinity of the tail neutral line in the expansive phase of substorms. Laboratory and satellite evidence are used to estimate this electric potential for substorms at earth; values of 500 kilovolts to 2 megavolts are calculated, in agreement with particle observations. It is further suggested that these particles, which have been accelerated in the night side magnetosphere, drift to the dayside on closed field lines, and under certain interplanetary conditions can escape to regions upstream of the bow shock

    Formation and evolution of the ionospheric plasma density shoulder and its relationship to the superfountain effects investigated during the 6 November 2001 great storm

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    This study investigates the 6 November 2001 great storm’s impact on the topside ionosphere utilizing data from the onboard TOPEX/Poseidon-NASA altimeter, Defense Meteorological Satellite Program–Special Sensor Ions, Electrons and Scintillation instruments and ACE interplanetary observatory. A set of field-aligned profiles demonstrate the storm evolution, caused by the precursor and promptly penetrating interplanetary eastward electric (E) fields, and strong equatorward winds reducing chemical loss, during the long-duration negative BZ events. At daytime-evening, the forward fountain experienced repeated strengthening, as the net eastward E field suddenly increased. The resultant symmetrical equatorial anomaly exhibited a continuous increase,while the energy inputs at both auroral regions were similar. In both hemispheres, by progressing poleward, a midlatitude shoulder exhibiting increased plasma densities, a plasma-density dropoff (steep gradient) and a plasma depletion appeared. These features were maintained while the reverse fountain operated. At the dropoff, elevated temperatures indicated the plasmapause. Consequently, the plasma depletion was the signature of plasmaspheric erosion. In each hemisphere, an isolated plasma flow, supplying the minimum plasma, was detected at the shoulder. Plasmaspheric compression, due to the enhanced E fields, could trigger this plasma flow. Exhibiting strong longitudinal variation at evening-nighttime, the shoulder increased 306% over the southeastern Pacific, where the nighttime Weddell Sea Anomaly (WSA) appeared before the storm. There, the shoulder indicated the storm-enhanced equatorward section of the quiet time WSA. Owing to the substantial equatorward plasmapause movement, a larger poleward section of the quiet time WSA eroded away, leaving a large depletion behind. This study reports first these (northern, southern) plasma flows and dramatic storm effects on a nighttime WSA

    Ionospheric response to the corotating interaction region-driven geomagnetic storm of October 2002

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    Unlike the geomagnetic storms produced by coronal mass ejections (CMEs), the storms generated by corotating interaction regions (CIRs) are not manifested by dramatic enhancements of the ring current. The CIR-driven storms are however capable of producing other phenomena typical for the magnetic storms such as relativistic particle acceleration, enhanced magnetospheric convection and ionospheric heating. This paper examines ionospheric plasma anomalies produced by a CIR-driven storm in the middle- and high-latitude ionosphere with a specific focus on the polar cap region. The moderate magnetic storm which took place on 14–17 October 2002 has been used as an example of the CIR-driven event. Four-dimensional tomographic reconstructions of the ionospheric plasma density using measurements of the total electron content along ray paths of GPS signals allow us to reveal the large-scale structure of storm-induced ionospheric anomalies. The tomographic reconstructions are compared with the data obtained by digital ionosonde located at Eureka station near the geomagnetic north pole. The morphology and dynamics of the observed ionospheric anomalies is compared qualitatively to the ionospheric anomalies produced by major CME-driven storms. It is demonstrated that the CIR-driven storm of October 2002 was able to produce ionospheric anomalies comparable to those produced by CME-driven storms of much greater Dst magnitude. This study represents an important step in linking the tomographic GPS reconstructions with the data from ground-based network of digital ionosondes

    Resonance Broadening Induced Nonlinear Saturation of Kinetic Alfven Turbulence in the Interplanetary Plasma

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    The saturation of ion cyclotron Alfven turbulence excited by beam particles is investigated using resonance broadening theory. The stochastic scattering which decorrelates particles, includes both random acceleration by electric fields and a turbulent magnetic mirroring effect. Turbulent mirroring is shown to yield non-Gaussian corrections to the orbits even if the random electric and magnetic fields are Gaussian. The predicted steady-state turbulence level exhibits a peaked anglular distribution, with a maximum near Theta ~ 60 degrees.Comment: 5 pages (including 2 figures

    Mass-loading, pile-up, and mirror-mode waves at comet 67P/Churyumov-Gerasimenko

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    The data from all Rosetta plasma consortium instruments and from the ROSINA COPS instrument are used to study the interaction of the solar wind with the outgassing cometary nucleus of 67P/Churyumov-Gerasimenko. During 6 and 7 June 2015, the interaction was first dominated by an increase in the solar wind dynamic pressure, caused by a higher solar wind ion density. This pressure compressed the draped magnetic field around the comet, and the increase in solar wind electrons enhanced the ionization of the outflow gas through collisional ionization. The new ions are picked up by the solar wind magnetic field, and create a ring/ring-beam distribution, which, in a high-β plasma, is unstable for mirror mode wave generation. Two different kinds of mirror modes are observed: one of small size generated by locally ionized water and one of large size generated by ionization and pick-up farther away from the comet
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