Browsing by Author "Bass, Elizabeth"
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Item Open Access Day to night variation in meteor trail measurements: Evidence for a new theory of plasma trail evolution(American Geophysical Union, 2008-02-06) Oppenheim, Meers M.; Sugar, Glenn; Bass, Elizabeth; Dimant, Yakov S.; Chau Chong Shing, Jorge LuisA recent theory of meteor trail plasma diffusion made the prediction that meteors will generate more and longer lasting non‐specular echoes at night than during the day. This letter presents the first evidence of a dramatic day to night difference in non‐specular meteor trail occurrence rates and their duration. These observations were made by the 50MHz radar at the Jicamarca Radio Observatory (JRO) in Peru. In one 20 minute period starting 95 minutes before sunrise, this radar detected 1288 head echoes and 341 trails while a similar time after dawn, it measured 1240 head echoes but only 50 trails. Also, the duration of the nighttime trails greatly exceeded the daytime ones. This pattern was confirmed by a second experiment in July 2007. This data provides strong evidence that it is necessary to account for the effect of the ionospheric plasma density to explain meteor diffusion.Item Restricted Improving the accuracy of meteoroid mass estimates from head echo deceleration(Springer, 2007-12) Bass, Elizabeth; Oppenheim, Meers; Chau Chong Shing, Jorge Luis; Olmstead, AliceThis paper examines current techniques used to determine meteoroid mass from high-power, large aperture (HPLA) radar observations. We demonstrate why the standard approach of fitting a polynomial to velocity measurements gives inaccurate results by applying this technique to artificial datasets. We then suggest an alternate approach, fitting velocity data to an ablation model. Using data taken at the Jicamarca Radio Observatory in July 2005, we compare the results of both methods and demonstrate that fitting velocity data to an ablation model yields a reasonable result in some instances where alternate methods produce physically unrealistic mass estimates.Item Open Access Mass distributions found using the Jicamarca Radio Observatory(Instituto Geofísico del Perú, 2010) Bass, Elizabeth; Oppenheim, Meers; Chau Chong Shing, Jorge LuisDiapositivas presentadas en el 2010 CEDAR Workshop, University of Colorado, Boulder, CO, 20-25 June 2010.Item Open Access Measuring MLT winds by tracking meteor trails with incoherent scatter radar: a new method observes rapidly changing winds exceeding 500km/Hr(Instituto Geofísico del Perú, 2009) Oppenheim, Meers; Sugar, Glenn; Slowey, Nick; Bass, Elizabeth; Chau Chong Shing, Jorge Luis; Close, SigridDiapositivas presentadas en: CEDAR Workshop 2009 del 28 de junio al 2 de julio de 2009 en Santa Fe, Nuevo México, USA.Item Open Access Meteor observations as a method of determining atmospheric properties(Instituto Geofísico del Perú, 2008) Bass, Elizabeth; Oppenheim, Meers; Sugar, GlennDiapositivas presentadas en: ISEA 12 - 12th International Symposium on Equatorial Aeronomy, May 18-24, 2008. Crete, Greece.Item Open Access Remote sensing lower thermosphere wind profiles using non-specular meteor echoes(American Geophysical Union, 2009-05-12) Oppenheim, Meers M.; Sugar, Glenn; Slowey, Nicholas O.; Bass, Elizabeth; Chau Chong Shing, Jorge Luis; Close, SigridThis article describes a new method of measuring wind velocity profiles between 93 km and 110 km altitude by tracking non‐specular meteor echoes as neutral winds transport the plasma trails. This requires a large VHF radar with interferometric capability able to point nearly perpendicular to the geomagnetic field. A small data sample from the Jicamarca Radio Observatory allows the measurement of horizontal wind speeds and directions with a range resolution of a few hundred meters. These observations show speeds reaching 150 m/s and sometimes changing by as much as 100 m/s over a 6 km altitude range. At the best times, these measurements can be made with only a few minutes of data. With some refinement of the data collection and analysis techniques, this technique should produce high resolution images of lower thermospheric winds as they change in both altitude and time.Item Open Access Using non-spectacular radar meteor echoes to monitor lower thermosphere wind profiles(Instituto Geofísico del Perú, 2009) Oppenheim, Meers; Sugar, Glenn; Bass, Elizabeth; Slowey, Nick; Chau Chong Shing, Jorge Luis; Close, SigridWe present a new method of measuring lower thermospheric wind velocity profiles by tracking non‐specular meteor echoes in time. This approach relies on having a radar following plasma irregularities as they are dragged by the neutral wind. This requires a VHF radar with interferometric capability able to point close to perpendicular to the geomagnetic field. Using a small sample of data from the Jicamarca Radio Observatory, we calculated wind speeds and directions between 90 and 110\ km with a range resolution of a few hundred meters. The measurements taken show speeds reaching 150m/s and someAmes changing by as much as 100m/s over a 6km altitude range. With some refinement of the data collection and analysis techniques, we expect that one could obtain high resolution images of lower thermospheric winds as they change in both altitude and time. We will discuss these results, the physics underlying these measurements, and the limitations.