Browsing by Author "Kelley, Michael C."
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Item Restricted By‐dependent prompt penetrating electric fields at the magnetic equator(American Geophysical Union, 2002-04-13) Kelley, Michael C.; Makela, Jonathan J.We propose a new type of prompt penetrating electric field effect which seems to be related to the y‐component of the interplanetary magnetic field and the NBZ current system. We report an equatorial electric field pattern which is not consistent with present understanding of prompt penetrating electric fields. The associated unbalanced excess NBZ current in one hemisphere partially flows across the nighttime equatorial zone. We find that a current system closes perpendicular to the ecliptic plane in the solar wind with a direction opposite to the interplanetary electric field. This is required for an MHD generator located in the solar wind.Item Restricted Convective ionospheric storms: a major space weather problem(American Geophysical Union, 2006-02-07) Kelley, Michael C.; Makela, Jonathan J.; De La Beaujardiére, OdileSome 50 years into the space age, technical societies are deeply committed to the utilization of space. For the military, space is the ultimate high ground from which a variety of surveillance, communications, and navigation systems operate. For industry, the communications and positional/navigational opportunities using space-based systems are virtually unlimited. However, when the plasma between the satellite and the receiver is turbulent, satellite signals scintillate in a manner analogous to the twinkling of starlight as it traverses the turbulent atmosphere, and both communication and navigation systems can be seriously affected. With the rapidly developing use of space assets comes the realization that ionospheric plasma, through which communications and navigation signals must pass, is not a benign medium. The most severe ionospheric weather occurs within +/-20° of the geomagnetic equator where stored gravitational energy sometimes is released after sunset, depending on the condition of the equatorial ionosphere, to form vast plumes of turbulent plasma. The plumes rise quickly in a manner analogous to thunderstorm convection and, due to their electrical properties, are transmitted rapidly for vast distances north and south along the Earth's magnetic field. Termed convective ionospheric storms (CIS), to emphasize the analogy of the ionospheric process to thunderstorms, these plumes are caught up in the high-speed eastward plasma drift and often last until well after midnight. As a result, a single storm can affect a very large area in its lifetime. To fully understand the problems posed by CIS, a detailed explanation of what is currently known about this topic is provided here, along with the methods for CIS monitoring. Weaknesses in scientific theory and monitoring capacities are also discussed.Item Restricted Convective ionospheric storms: A review(American Geophysical Union, 2011-06-22) Kelley, Michael C.; Makela, Jonathan J.; de la Beaujardiére, Odile; Retterer, JohnEquatorial spread F (ESF) was discovered almost a century ago using the first radio wave instrument designed to study the upper atmosphere: the ionosonde. The name came from the appearance of reflections from the normally smooth ionosphere, which were spread over the altitude frequency coordinates used by the instrument. Attempts to understand this phenomenon in any depth activated such tools as radars and in situ probes such as rockets and satellites in the 1960s. Over the next 15 years, these tools expanded our experimental understanding enormously, and new nonlinear theoretical methods developed in the late 1970s, which led to proposing a name revision from ESF to convective ionospheric storms. Interest in these phenomena continues, but a new, practical aspect has developed from the associated turbulence effects on communications (transionosphere) and navigation (GPS). The first satellite to specifically investigate this problem and the associated goal of predicting occurrences is under the umbrella of the Communications/Navigation Outage Forecast System (C/NOFS). In contemplating the successful first years of the C/NOFS program, reviewing the state of the art in our knowledge of convective ionospheric storms seems appropriate. We also present some initial results of this satellite program. A major goal of the National Space Weather Program, and of C/NOFS, is predicting these storms, analogous to thunderstorms in the lower atmosphere due to their adverse effects on communication and navigation signals. Although ambitious, predictive capability is a noble and important goal in the current technological age and is potentially within our reach during the coming decade.Item Restricted Evidence for anomalous cowling conductivity in the strongly driven equatorial electrojet and a reconciliation of magnetic field data with theory(Editor no identificado, 2009-08) Kelley, Michael C.; Ilma, Ronald R.; Alken, Patrick; Maus, StefanSeveral days of continuous incoherent scatter radar observations during the November 2004 magnetic superstorm are available, as well as data from the CHAMP [CHAllenging Minisatellite Payload] satellite magnetic fiel d detector. We have found that, for zonal electric fields greater than about 1 mV/m, the linear relationship between CHAMP-deduced electric fields and Jicamarca-measured electric fields breaks down. We find that the observed magnetic field is a factor of two smaller than expected for the largest zonal electric field (3.2 mV/m) observed simultaneously in time and nearby spatially with CHAMP. The fact that similar decreases in the effective conductivity occurred during both normal and counter-electrojet conditions indicates that Farley-Buneman waves must be the source of the physical mechanism for the reduced current. In addition, we provide an explanation for a long standing (more than 35 years) discrepancy between theory and (rocket) experiments, concerning the peak height of the electrojet and the magnetic field perturbation. The correction by a factor of four of the electron-neutral collision frequency thought to explain this problem is not necessary if the field line integrated conductivities are used.Item Open Access Investigation of the feasibility of meteoric smoke detection with Jicamarca(Instituto Geofísico del Perú, 2009-06) Varney, Roger H.; Kelley, Michael C.; Chau Chong Shing, Jorge LuisDiapositivas presentadas en: CEDAR Workshop 2009 del 28 de junio al 2 de julio de 2009 en Santa Fe, Nuevo México, USA.Item Restricted Long‐duration penetration of the interplanetary electric field to the low‐latitude ionosphere during the main phase of magnetic storms(American Geophysical Union, 2005-11-26) Huang, Chao-Song; Foster, John C.; Kelley, Michael C.It is well known that the interplanetary electric field can penetrate to the low‐latitude ionosphere. It is generally believed that the penetration of electric fields can last only for ∼30 min because of the shielding effect in the ring current. In this paper we present the observations of the dayside ionospheric electric field enhancements at middle and low latitudes in association with reorientations of the interplanetary magnetic field (IMF). In six cases, the eastward electric field in the dayside equatorial ionosphere, measured by the Jicamarca incoherent scatter radar, was enhanced for 2–3 hours after the IMF turned southward and remained continuously southward. In one case the eastward electric field in the dayside midlatitude ionosphere, measured by the Millstone Hill incoherent scatter radar, was continuously enhanced for ∼10 hours during southward IMF. Since Millstone Hill is close to the equatorward boundary of the auroral zone during magnetic storms, the penetration electric field there may be different from that at the equatorial ionosphere. The most striking feature of the measurements is that the enhancements of the ionospheric electric field can last for many hours without significant decay. The electric field enhancements in the middle‐ and low‐latitude ionosphere are closely related to magnetic activity and occur during the main phase of magnetic storms. The observations show that the interplanetary electric field can continuously penetrate to the low‐latitude ionosphere without shielding for many hours as long as the strengthening of the magnetic activity is going on under storm conditions.Item Restricted Mid-latitude ionospheric fluctuation spectra due to secondary E x B instabilities(Elsevier, 2004-09-03) Kelley, Michael C.; Swartz, Wesley E.; Makela, Jonathan J.The most spectacular night of mid-latitude spread F ever recorded at Arecibo is analyzed and compared with barium cloud observations made in the 1970s and with equatorial spread F. Strong evidence is found for a secondary instability driven either by a poleward electric field and a westward density gradient (both presumably due to a primary Perkins instability), or by a zero-order eastward wind flowing across the westward gradient. Spectra computed from the incoherent scatter density profiles of this event are very similar to the spectra of both barium striations and equatorial spread F. Estimates of the strength of the radar wave scattering expected from the fluctuation spectra are in good agreement with the VHF observations from that night. Finally, a poleward-surging, mid-latitude plasma bubble is seen to bifurcate in a manner similar to equatorial spread-F simulations.Item Restricted Mid-latitude plasma and electric field measurements during space weather month, September 1999(Elsevier, 2003-07) Makela, Jonathan J.; Kelley, Michael C.; González, Sixto A.; Aponte, Nestor; Sojka, Jan J.Using data collected during the September 1999 combined ionospheric campaign (CIC), we examine the effects of moderate geomagnetic activity on low and mid-latitudes. Perturbations in the zonal electric field, measured at both Jicamarca and Arecibo, are the most striking aspect of this data. These eastward electric fields resulted in a poleward advection of the Appleton anomaly to mid-latitudes, where it was observed as a gradient in the nighttime electron density, as measured by the Arecibo incoherent scatter radar. This gradient was severe enough that it was observable in airglow measurements at 630.0 and . To put this data into context, we also examine the worldwide conditions during this time period and find evidence for several substorms, penetrating electric fields, and disturbance dynamo electric fields.Item Restricted Observations of electric fields associated with internal gravity waves(American Geophysical Union, 2009-02-07) Varney, Roger H.; Kelley, Michael C.; Kudeki, ErhanAt the Jicamarca Radio Observatory, the vertical drift component yields a very accurate measure of the eastward electric field. Occasionally, this drift component displays a downward phase progression, evidence for a relationship to a gravity wave. We examined the Jicamarca database for events of this type and made an attempt to determine the properties of the associated waves. The only measurables we have are the amplitudes, the frequency in the Earth‐fixed frame, and the vertical wavelength. In order to avoid shorting by the current along magnetic field lines, we argue that the propagation must be close to pure zonal. We then use measurements or models of the zonal plasma drift and argue that the zonal wind should be in the same direction and about 15% higher. Using this estimate, we then determine the frequency in the wind frame by solving the dispersion relation for gravity waves and the Doppler‐shift equation simultaneously. Typical values for the horizontal wavelength, vertical wavelength, and period in the wind frame are 600 km, 350 km, and 25 min, respectively. The typical gravity wave‐induced vertical drift perpendicular to B in these events is a few meters per second. This is marginal at best for seeding the Rayleigh‐Taylor instability. However, larger‐amplitude events may be masked by the development of the plumes themselves. All but two events found thus far occurred at night but the daytime cases are fascinating since the E region is expected to short out such fields.Item Restricted On the development of nonlinear waves in the equatorial electrojet(Elsevier, 2013-10) Kelley, Michael C.; Ilma, Ronald R.Theories for the equatorial electrojet (EEJ) have been notoriously difficult to resolve with data. Two of these problems were solved recently and another is discussed in this publication. We initially review solutions to the first two issues: the constant phase velocity of 3 m waves in the EEJ with zenith angle and the disagreement between the observed and calculated altitude of the EEJ current. One remaining problem is the nonlinear nature of large-scale waves in the electrojet that appear as square waves. One possibility is the conversion of free energy into ion acoustic waves, which limits the large-scale wave amplitude to the threshold for producing such waves. Another is the breaking of large-scale waves when the perturbation velocity internal to the wave approaches the wave phase velocity.Item Restricted Penetration electric fields: Efficiency and characteristic time scale(Elsevier, 2007-07) Huang, Chao-Song; Sazykin, Stanislav; Chau Chong Shing, Jorge Luis; Maruyama, Naomi; Kelley, Michael C.Penetration of the interplanetary electric field (IEF) to the middle- and low-latitude ionosphere has been investigated for nearly four decades. Most previous studies focused on the correlation between the interplanetary and ionospheric electric field perturbations. Very little attention has been paid to a quantitative relationship except for a recent case analysis by Kelley et al. [2003. Penetration of the solar wind electric field into the magnetosphere/ionosphere system. Geophysical Research Letters 30(4), 1158. doi:10.1029/2002GL016321]. In this paper, we present a statistical result of the efficiency of IEF penetration to the dayside equatorial ionosphere; the efficiency is defined as the ratio of the change of the equatorial ionospheric electric field to the change of the IEF. The Jicamarca incoherent scatter radar has made continuous operation with a coherent scatter mode since 2001, and the radar data of equatorial ionospheric electric fields are used in our statistics. On the basis of data statistics, we derive an empirical value of 9.6% for the efficiency of penetration. We apply this empirical formula to the observations and numerical simulations of storm-time penetration electric fields over a prolonged interval of southward interplanetary magnetic field. The prediction of the formula is in good agreement with case studies and with results from first-principle simulations of the coupled magnetosphere–ionosphere–thermosphere system. We conclude that the IEF can continuously penetrate to the low-latitude ionosphere without significant attenuation for many hours during the main phase of magnetic storms.Item Open Access Penetration of the solar wind electric field into the magnetosphere/ionosphere system(American Geophysical Union, 2003-02-19) Kelley, Michael C.; Makela, Jonathan J.; Chau Chong Shing, Jorge Luis; Nicolls, Michael J.On April 17, 2002 an intense, long duration electric field penetration event was captured by the Jicamarca incoherent scatter radar. Other radars in the U. S. chain detected the event as well, although not with as much clarity. The Interplanetary Electric Field (IEF) is available from the ACE satellite as well. The ratio of the dawn‐to‐dusk component of the IEF to the dawn‐to‐dusk electric field in the equatorial ionosphere for periods less than about two hours is 15:1. We suggest that this corresponds to the ratio of the size of the magnetosphere to the length of the connection line between the Interplanetary Magnetic Field (IMF) and the Earth's magnetic field. Simultaneous magnetic field measurements at Piura (off the magnetic equator) and at Jicamarca (under the magnetic equator) in Peru, reveal the same high frequency components and suggest that a chain of stations or an equatorial fleet of satellites in low earth orbit could be used to monitor the connection length continuously.Item Open Access Polar mesosphere summer echo studies at 51.5 MHz at Resolute Bay, Canada: Comparison with Poker Flat results(American Geophysical Union, 2001-11) Huamán, Mercedes M.; Kelley, Michael C.; Hocking, Wayne K.; Woodman Pollitt, Ronald FranciscoWe present a study of seasonal and diurna! variations of polar mesosphere summer echoes (PMSE), along with temperature and wind data collected during summer 1998 using the 51.5 MHz VHF radar located in Resolute Bay, Canada (75°N, 95°W). The latitudinal dependence of PMSE occurrence and strength are examined by comparing Resolute Bay observations with earlier Poker Flat (65°N, 147°W) observations. Temperatures measurements at Resolute Bay using the radar in the meteor mode are compared with satellite measurements at similar latitudes ofResolute Bay and Poker Flat. The temperature measurements are in good agreement, and, as expected, PMSE is strongly controlled by the seasonal temperature variations. Differences found in the daily composite and monthly average winds, and in the monthly evolution of the amplitudes and phases of the diurna! and semidiurnal tides at Resolute Bay and Poker Flat, are discussed in order to establish the role that they play in the occurrence of PMSE. In general, we find that the diurna! occurrence of PMSE at Resolute Bay also follows the diurna! variation of temperature. The echoes tend to occur more frequently and with greatest intensity when the temperatures are the coldest, in a period centered around local noon. We show that the diurna! wind components at Resolute Bay appear to correlate with the occurrence of PMSE, as also seen at Poker Flat. PMSE at Resolute Bay are not as strong or as frequent as reported at Poker Flat, differing with what we had expected since strongest and more frequent echoes have been observed in the European sector approaching the pole. New observations are needed to establish a possible longitudinal dependence of PMSE occurrence given that the present American sector data are compared with data taken over 10 years ago.Item Restricted Spectacular low- and mid-latitude electrical fields and neutral winds during a superstorm(Elsevier, 2010-03) Kelley, Michael C.; Ilma, Ronald R.; Nicolls, Michael; Erickson, Phillip; Goncharenko, Larisa; Chau Chong Shing, Jorge Luis; Aponte, Nestor; Kozyra, Janet U.In November 2004, a major magnetic storm occurred, a lengthy portion of which was recorded by the Upper Atmospheric Radar Chain. On the 9th and 10th, the Jicamarca Radar detected the highest magnitude penetrating electric fields (±3 mV/m) and vertical drifts (±120 m/s) ever seen at this premiere facility. These large and variable drifts were highly correlated with the interplanetary magnetic and electric fields and created a double F layer on the dayside and unusual TEC behavior throughout the low-latitude zone. These solar wind-induced drifts both suppressed and generated irregularities at the magnetic equator at different times. Large-scale thermospheric disturbances were generated by high-latitude heating and tracked through the middle- to low-latitude zones where both parallel and perpendicular plasma drifts created major ionospheric changes. The auroral oval was located at a magnetic L shell of about three for many hours.Item Restricted The spectral properties of low-latitude daytime electric fields inferred from magnetometer observations(Elsevier, 2007-03-24) Nicolls, Michael J.; Kelley, Michael C.; Chau Chong Shing, Jorge Luis; Veliz, Oscar; Anderson, David; Anghel, AdelaFour years of magnetometer data from two locations in Peru, one at the equator and one off the equator, have been converted to electric fields and their frequency characteristics (fluctuation spectra) examined. In the frequency range from 0.1 to 30 cycles per hour, the average spectrum monotonically decreases. However, it deviates from a power law in the range 0.3–3 cycles per hour especially for high levels of activity. The integrated power above 0.15 cycles per hour is a strong function of Kp indicating that much of the fluctuations in the ionospheric equatorial field are of solar wind or magnetospheric origin. This result is in agreement with a previous power spectral study of low, middle, and high latitude fields using radars. The observed field strengths are lower than the ones observed in a previous study using balloon data at middle and high latitudes when the fields are projected to the equatorial plane. Simultaneous interplanetary electric field (IEF) data are compared to the equatorial field to determine how strong a relationship exists and to determine the amplitude and phase of their ratio as a function of frequency—an estimate of the average transfer function of the system. This function displays a bandpass-like form with a peak near 0.5 cycles per hour. This peak and evidence for a ringing of the time domain response suggests a weakly resonant system indicating some capacitance in addition to the inductance of the ring current and the resistance of the ionosphere. Case studies show that application of this function to IEF data yields good results and supports the notion that the response of the equatorial field to long-duration IEF polarities can last for many hours. Application of the function to test inputs such as pulses and triangle waves support this result. At high frequencies, we suggest that mapping of small-scale MHD turbulence is less effective than high frequency related transitions in the IEF.