Showing papers by "Ramon Lopez published in 2013"

Theoretical study: Influence of different energy sources on the cusp neutral density enhancement

Abstract: [1] Simulations with the Global Ionosphere-Thermosphere Model (GITM) show that both Poynting flux and soft electron precipitation are important in producing neutral density enhancements near 400 km altitude in the cusp that have been observed by the Challenging Minisatellite Payload (CHAMP) satellite. Imposing a Poynting flux of 75 mW/m2 in the cusp within the model increases the neutral density by 34%. The direct heating from 100 eV, 2 mW/m2 soft electron precipitation produces only a 5% neutral density enhancement at 400 km. However, the associated enhanced ionization in the F-region from the electron precipitation leads to a neutral density enhancement of 24% through increased Joule heating. Thus, the net effect of the soft electron is close to 29%, and the combined influence of Poynting flux and soft particle precipitation causes a more than 50% increase in neutral density at 400 km, which is consistent with CHAMP observations in extreme cases. The effect of electron precipitation on the neutral density at 400 km decreases sharply with increasing characteristic energy such that 900 eV electrons have little effect on neutral density. Finally, the impact of 2 keV, 0.3 mW/m2 proton precipitation on the neutral density is negligible due to a lowering of the altitude of Joule heating.

Government Spending and Air Pollution in the US

Abstract: This study examines the effect of the composition of federal and state government spending on various important air pollutants in the US using a newly assembled data set of government spending. The results indicate that a reallocation of spending from private goods (RME) to social and public goods (PME) by state and local governments reduces sulfur dioxide concentrations while the composition of federal spending has no effect. A 10% percent increase in the share of state and local social and public goods government spending reduces air pollution concentrations by 3 to 5% for Sulfur Dioxide, 2 to 3% for particulate matter 2.5 and 1 to 2 % for ozone. The results are robust to various sensitivity checks.

Simulation of the March 9, 1995 substorm and initial comparison to data

Abstract: In this study we examine a period of substorm activity that occurred on March 9, 1995. Using solar wind data as input, the event has been simulated using a 3-D MHD code. To determine how well the simulation fared, we have compared the simulation results to data. This comparison has taken two forms. The first is a comparison to individual spacecraft in the magnetotail. The second is a comparison of global energy storage and release, where we have compared the auroral heating to data-based estimates of auroral energy dissipation, as well as evaluating the variation of the open flux in the simulation. There is a generally good level of agreement between the simulation results and data. Thus our results show that MHD simulations can be used to model at least one magnetospheric substorm.

Influence of the Orinoco River on the primary production of eastern Caribbean surface waters

Abstract: [1] The influence of the Orinoco River on the primary production in eastern Caribbean waters was investigated using fast repetition rate fluorometry (FRRF) and ocean color remote sensing. FRRF-based carbon fixation rates significantly correlated with independent estimates based on the 14C uptake method (r = 0.92, n = 9). Satellite-derived estimates of primary production, using the Carbon Based Productivity Method (CbPM), moderately correlated with in situ FRRF-based measurements. These estimates varied with river plume dilution gradients, with the highest rates associated with waters under river plume influence (CbPM 631 mg C m−2 d−1 and FRRF 570 mg C m−2 d−1). A time series of satellite-derived estimates (2002–2011) revealed seasonal variations associated with river discharge and climate driven fluctuations. Regional integrated productivity of about 2.80 Tg C yr−1 was calculated based on the average spatial coverage of the Orinoco River plume over the last decade.

Reduction of viscous potential for northward interplanetary magnetic field as seen in the LFM simulation

Abstract: [1] The two primary methods responsible for solar wind magnetosphere coupling are magnetic reconnection and the viscous interaction. The viscous interaction is generated due to the antisunward dragging of plasma inside the magnetopause by the plasma flowing in the magnetosheath, creating a return flow deeper inside the magnetosphere and producing a circulation pattern. This viscous circulation pattern is mapped into the ionosphere via magnetic field lines, which results in ionospheric electric field in the nonrotating Earth's frame. We measure this interaction in terms of an electric potential, the viscous potential. In this paper, we use the results obtained from the Lyon-Fedder-Mobarry (LFM) simulation model during periods of purely northward interplanetary magnetic field (IMF) for different solar wind velocity and ionospheric conductivity, showing a reduction of the viscous potential with increasing magnitude of northward IMF. The viscous potential is found to settle around 5–10 kV for large +Bz values. The decrease in viscous potential was found to be associated with a weak or nonexistent sunward plasma flow in the nightside plasmasheet. Instead, the return flow to the dayside occurs at high latitudes and is associated with the reconnection topology and dynamics that occur during northward IMF periods. We also show that the magnetosphere remains closed during purely northward IMF, except for two small regions—one on each hemisphere, where the magnetic reconnection occur. We argue that the reduction of the viscous potential is due to a reduction of the velocity shear across the magnetopause and the lack of sunward convection in the equatorial tail.

Simulated ring current response during periods of dawn‐dusk oriented interplanetary magnetic field (By)

Abstract: [1] Ring current formation is mainly attributed to enhanced global magnetospheric convection and particle injection. One of the indicators of enhanced global magnetospheric convection is the transpolar potential. The transpolar potential has been shown to respond to dawn-dusk oriented interplanetary magnetic field (IMF), enhancing as the IMF magnitude grows. This suggests that the ring current should respond to dawn-dusk oriented IMF. This work examines the ring current response during periods of dawn-dusk oriented IMF using the Lyon-Fedder-Mobarry and Comprehensive Ring Current Model simulations. Exploring three hypotheses, this work shows through simulation results that the ring current does respond during periods of dawn-dusk oriented IMF, that the inner magnetospheric response is different for periods of dawn-dusk oriented IMF than for periods of southward IMF, and that these differences are attributed to both lower magnetospheric convection on closed field lines and the location of the reconnection region on the nightside. Specifically, the simulation results show that as the magnitude of the dawn-dusk oriented IMF increases, producing a corresponding increase in the transpolar potential, the ring current response increases. The response is always much less than a comparable southward IMF would produce. This lower response is due to both magnetospheric convection on closed field lines, which builds the ring current but at a slower rate, and flank reconnection, which allows energy to flow through the inner magnetosphere without building the ring current plasma population (as a conduit).

Sustainable Economic Growth: Structural Transformation with Consumption Flexibility

Abstract: The standard theoretical literature has shown that environmental sustainability and positive economic growth are not incompatible as long as environmental policies are optimal. However, in showing this result earlier studies have relied on strong assumptions that may appear to charge the dice in favor of such result. Here we show that once the role of the consumption composition effect is recognized, environmentally sustainable economic growth may exist even if some of the most questionable assumptions used by the canonical models are relaxed. In particular, we show that sustainable growth is possible even if environmental and man-made factors of production are complement rather than highly substitutable as has been invariably assumed by the literature and even if technological change is entirely pollution-augmenting.

Sustainable Economic Growth: Structural Transformation with Consumption Flexibility

Abstract: The standard theoretical literature has shown that environmental sustainability and positive economic growth are not incompatible as long as environmental policies are optimal. However, in showing this result earlier studies have relied on strong assumptions that may appear to charge the dice in favor of such result. Here we show that once the role of the consumption composition effect is recognized, environmentally sustainable economic growth may exist even if some of the most questionable assumptions used by the canonical models are relaxed. In particular, we show that sustainable growth is possible even if environmental and man-made factors of production are complement rather than highly substitutable as has been invariably assumed by the literature and even if technological change is entirely pollutionaugmenting. JEL classification number: O44, Q01, Q56