Browsing by Author "Makela, Jonathan J."
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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 Comparison of zonal neutral winds with equatorial plasma bubble and plasma drift velocities(American Geophysical Union, 2013-03-20) Chapagain, Narayan P.; Fisher, Daniel J.; Meriwether, John W.; Chau Chong Shing, Jorge Luis; Makela, Jonathan J.A one-year dataset spanning March 2011-March 2012 of coincident observations of night time thermospheric zonal neutral winds, equatorial plasma bubble (EPB) velocities, and zonal plasma drifts are used to examine the relationship between the thermosphere and ionosphere near the geomagnetic equator over Peru. Thermospheric neutral winds are determined by using a bistatic Fabry–Perot interferometer (FPI) experiment located at Merihill and Nazca in Peru. The ambient plasma drift velocities were obtained using the incoherent scatter radar at the Jicamarca Radio Observatory in Peru. The EPB zonal velocities were estimated utilizing images of the OI 630.0-nm emission recorded by a narrow-field optical imaging system at the Cerro Tololo InterAmerican Observatory in Chile. The joint analysis of these datasets illustrates that the night time and night-to-night variations in the zonal neutral winds, EPB velocities, and plasma drifts are well correlated. This consistent result of the local time variations of the neutral winds with that of EPB and plasma drifts illustrates that the F-region dynamo is, in general, fully activated. However, at times, the magnitude of the EPB velocities and the plasma drifts are different from the neutral winds. It is plausible that such a difference is due either to the effect of polarization electric fields developed inside the EPB or due to the latitudinal gradient of the neutral winds and EPB velocity measurements since the EPB velocities are estimated at a higher latitude, corresponding to an apex altitude of ~400 km, than the wind estimates, which derive from an apex altitude of ~250 km.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 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 Open Access On the detection of a solar radio burst event that occurred on 28 August 2022 and its effect on GNSS signals as observed by ionospheric scintillation monitors distributed over the American sector(EDP Open, 2023-11-28) Wright, Isaac G.; Rodrigues, Fabiano S.; Gomez Socola, Josemaria; Moraes, Alison O.; Monico, João F. G.; Sojka, Jan; Scherliess, Ludger; Layne, Dan; Paulino, Igo; Buriti, Ricardo A.; Brum, Christiano G. M.; Terra, Pedrina; Deshpande, Kshitija; Vaggu, Pralay R.; Erickson, Philip J.; Frissell, Nathaniel A.; Makela, Jonathan J.; Scipión, DannyAs part of an effort to observe and study ionospheric disturbances and their effects on radio signals used by Global Navigation Satellite Systems (GNSS), alternative low-cost GNSS-based ionospheric scintillation and total electron content (TEC) monitors have been deployed over the American sector. During an inspection of the observations made on 28 August 2022, we found increases in the amplitude scintillation index (S4) reported by the monitors for the period between approximately 17:45 UT and 18:20 UT. The distributed, dual-frequency observations made by the sensors allowed us to determine that the increases in S4 were not caused by ionospheric irregularities. Instead, they resulted from Carrier-to-Noise (C/No) variations caused by a solar radio burst (SRB) event that followed the occurrence of two M-class X-ray solar flares and a Halo coronal mass ejection. The measurements also allowed us to quantify the impact of the SRB on GNSS signals. The observations show that the SRB caused maximum C/No fadings of about 8 dB-Hz (12 dB-Hz) on L1 ~ 1.6 GHz (L2 ~ 1.2 GHz) for signals observed by the monitor in Dallas for which the solar zenith angle was minimum (~24.4°) during the SRB. Calculations using observations made by the distributed monitors also show excellent agreement for estimates of the maximum (vertical equivalent) C/No fadings in both L1 and L2. The calculations show maximum fadings of 9 dB-Hz for L1 and of 13 dB-Hz for L2. Finally, the results exemplify the usefulness of low-cost monitors for studies beyond those associated with ionospheric irregularities and scintillation.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 Restricted Recent advances in equatorial, low- and mid-latitude aeronomy(Elsevier, 2013-10) Bhattacharyya, Archana; Chau Chong Shing, Jorge Luis; Denardini, Clezio M.; Hysell, David L.; Makela, Jonathan J.; Shiokawa, Kazuo; Kudeki, ErhanThis special issue of the Journal of Atmospheric and Solar–Terrestrial Physics on “Recent Advances in Equatorial, Low- and Mid-latitude Aeronomy” contains selected papers presented at the 13th International Symposium on Equatorial Aeronomy (ISEA13). This symposium is the latest in a long series of ISEAs, which was started in 1962 soon after the Jicamarca Radio Observatory (JRO) began its operation near Lima, Peru. The first ISEA was held in Huaychulo, Peru; and since then the symposium has been held every 3–5 years at different locations around the globe, bringing together scientists from all over the world, who are interested in the low- and mid-latitude atmosphere and ionosphere, and their coupling to other latitudes and altitudes. The ISEAs have become important events for researchers working in this field, as it offers them an opportunity to share their most recent results and discuss new techniques and possibilities for future coordinated campaigns and experiments.