The European Commission has a mandate from the EU's Renewable Energy and Fuel Quality Directives ... more The European Commission has a mandate from the EU's Renewable Energy and Fuel Quality Directives to propose a methodology, consistent with the best available science, to address indirect land use change (iLUC). One proposed solution to the iLUC problem is the application of iLUC factors in European fuels policyit is widely expected that should the EU adopt such iLUC factors, they would be based on iLUC modelling using the International Food Policy Research Institute's (IFPRI) MIRAGE model. Taking the iLUC factors from IFPRI MIRAGE as our central estimate, we use Monte Carlo analysis on a simple model of potential biofuel pathways for Europe to assess the likely average carbon saving from three possible European biofuel policy scenarios: no action on iLUC; raised GHG thresholds for direct emissions savings; and the introduction of iLUC factors. We find that without iLUC factors (or some other effective iLUC minimization approach) European biofuel mandates are unlikely to deliver significant GHG emissions benefits in 2020, and have a substantial probability of increasing net GHG emissions. In contrast, the implementation of iLUC factors is likely to significantly increase the carbon savings from EU biofuel policy. With iLUC factors, it is likely that most permitted pathways would conform to the Renewable Energy Directive requirement for a minimum 50% GHG reduction compared to fossil fuels.
ABSTRACT Observations have shown the connection between oscillations within the sunspot photosphe... more ABSTRACT Observations have shown the connection between oscillations within the sunspot photosphere and photospheric p-modes. In the strong, vertical, magnetic field regions of sunspot umbrae, it is thought that these acoustic p-modes undergo mode conversion to slow-magnetoacoustic waves, and that these slow-magnetoacoustic p-modes may be waveguided from the photosphere into the solar corona along the magnetic field. Observations are presented of the propagation of these waves and their channelling into the coronal parts of magnetic loops, originally emerging from a sunspot region. These observations are combined with 2-D MHD numerical simulations of wave leakage and direct propagation within the model sunspot atmosphere. The simulations are driven at the photospheric level by the Doppler velocity field of p-modes observed within the sunspot, and the response of forward modelling of the atmosphere is compared to observations. In the future, this combined approach of observation and theoretical modelling may be exploited to allow magneto-seismology of the solar atmosphere above sunspots or active regions. M.S. Marsh supported through the NASA post doctoral program.
Magnetic coupling through MHD waves and oscillations at the solar interior -lower corona interfac... more Magnetic coupling through MHD waves and oscillations at the solar interior -lower corona interface is studied here. First, the effect of a magnetic solar atmosphere on solar global oscillations is investigated. Frequency shifts of acoustic eigenmodes are found due to the presence of the chromospheric and coronal magnetic fields. Potential application to local magneto-seismology is highlighted.
The leakage and coupling of solar global oscillations to the overlaying magnetized solar atmosphe... more The leakage and coupling of solar global oscillations to the overlaying magnetized solar atmosphere is investigated in this paper. Solar global acoustic oscillations may couple through resonant absorption to atmospheric local magnetic eigenoscillations (i) resulting in small shifts of the order of µHz in the real part of their frequencies as compared to their non-magnetic counterparts, and (ii) causing dissipation of wave energy and a consequent line broadening of the modes. Alternatively, global modes may also penetrate deeply into the magnetized solar atmosphere through leakage along magnetic field lines causing small-scale structuring in the transition region and low corona. By analyzing the dynamic fragmentation generated by direct wave propagations, one may deduce diagnostic information about the geometric and physical properties of the local magnetic environment in the atmosphere. A few numerical examples are presented here to demonstrate the leakage of global oscillations and its influence and omnipotence on the dynamics of the lower solar atmosphere.
Aims. This paper aims to look at the propagation of synthetic photospheric oscillations from a po... more Aims. This paper aims to look at the propagation of synthetic photospheric oscillations from a point source into a two-dimensional non-magnetic solar atmosphere. It takes a particular interest in the leakage of 5-min global oscillations into the atmosphere, and aims to complement efforts on the driving of chromospheric dynamics (e.g. spicules and waves) by 5-min oscillations. Methods. A model solar atmosphere is constructed based on realistic temperature and gravitational stratification. The response of this atmosphere to a wide range of adiabatic periodic velocity drivers is numerically investigated in the hydrodynamic approximation.
The European Commission has a mandate from the EU's Renewable Energy and Fuel Quality Directives ... more The European Commission has a mandate from the EU's Renewable Energy and Fuel Quality Directives to propose a methodology, consistent with the best available science, to address indirect land use change (iLUC). One proposed solution to the iLUC problem is the application of iLUC factors in European fuels policyit is widely expected that should the EU adopt such iLUC factors, they would be based on iLUC modelling using the International Food Policy Research Institute's (IFPRI) MIRAGE model. Taking the iLUC factors from IFPRI MIRAGE as our central estimate, we use Monte Carlo analysis on a simple model of potential biofuel pathways for Europe to assess the likely average carbon saving from three possible European biofuel policy scenarios: no action on iLUC; raised GHG thresholds for direct emissions savings; and the introduction of iLUC factors. We find that without iLUC factors (or some other effective iLUC minimization approach) European biofuel mandates are unlikely to deliver significant GHG emissions benefits in 2020, and have a substantial probability of increasing net GHG emissions. In contrast, the implementation of iLUC factors is likely to significantly increase the carbon savings from EU biofuel policy. With iLUC factors, it is likely that most permitted pathways would conform to the Renewable Energy Directive requirement for a minimum 50% GHG reduction compared to fossil fuels.
ABSTRACT Observations have shown the connection between oscillations within the sunspot photosphe... more ABSTRACT Observations have shown the connection between oscillations within the sunspot photosphere and photospheric p-modes. In the strong, vertical, magnetic field regions of sunspot umbrae, it is thought that these acoustic p-modes undergo mode conversion to slow-magnetoacoustic waves, and that these slow-magnetoacoustic p-modes may be waveguided from the photosphere into the solar corona along the magnetic field. Observations are presented of the propagation of these waves and their channelling into the coronal parts of magnetic loops, originally emerging from a sunspot region. These observations are combined with 2-D MHD numerical simulations of wave leakage and direct propagation within the model sunspot atmosphere. The simulations are driven at the photospheric level by the Doppler velocity field of p-modes observed within the sunspot, and the response of forward modelling of the atmosphere is compared to observations. In the future, this combined approach of observation and theoretical modelling may be exploited to allow magneto-seismology of the solar atmosphere above sunspots or active regions. M.S. Marsh supported through the NASA post doctoral program.
Magnetic coupling through MHD waves and oscillations at the solar interior -lower corona interfac... more Magnetic coupling through MHD waves and oscillations at the solar interior -lower corona interface is studied here. First, the effect of a magnetic solar atmosphere on solar global oscillations is investigated. Frequency shifts of acoustic eigenmodes are found due to the presence of the chromospheric and coronal magnetic fields. Potential application to local magneto-seismology is highlighted.
The leakage and coupling of solar global oscillations to the overlaying magnetized solar atmosphe... more The leakage and coupling of solar global oscillations to the overlaying magnetized solar atmosphere is investigated in this paper. Solar global acoustic oscillations may couple through resonant absorption to atmospheric local magnetic eigenoscillations (i) resulting in small shifts of the order of µHz in the real part of their frequencies as compared to their non-magnetic counterparts, and (ii) causing dissipation of wave energy and a consequent line broadening of the modes. Alternatively, global modes may also penetrate deeply into the magnetized solar atmosphere through leakage along magnetic field lines causing small-scale structuring in the transition region and low corona. By analyzing the dynamic fragmentation generated by direct wave propagations, one may deduce diagnostic information about the geometric and physical properties of the local magnetic environment in the atmosphere. A few numerical examples are presented here to demonstrate the leakage of global oscillations and its influence and omnipotence on the dynamics of the lower solar atmosphere.
Aims. This paper aims to look at the propagation of synthetic photospheric oscillations from a po... more Aims. This paper aims to look at the propagation of synthetic photospheric oscillations from a point source into a two-dimensional non-magnetic solar atmosphere. It takes a particular interest in the leakage of 5-min global oscillations into the atmosphere, and aims to complement efforts on the driving of chromospheric dynamics (e.g. spicules and waves) by 5-min oscillations. Methods. A model solar atmosphere is constructed based on realistic temperature and gravitational stratification. The response of this atmosphere to a wide range of adiabatic periodic velocity drivers is numerically investigated in the hydrodynamic approximation.
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Papers by Chris Malins