During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with ampl... more During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with amplitudes up to more than ~240 mV/m were observed by the Time Domain Sampler of the STEREO S/Waves instrument. These waves are an order of magnitude larger than previously been observed for whistlers in the radiation belt.
During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with ampl... more During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with amplitudes up to more than ~240 mV/m were observed by the Time Domain Sampler of the STEREO S/Waves instrument. These waves are an order of magnitude larger than previously been observed for whistlers in the radiation belt.
1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of ... more 1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of energy into the auroral ionosphere from broadband ULF waves in the cusp and low-latitude boundary layer. A comparison of the wave Poynting flux with particle energy and flux at both satellites indicates that energy transfer from the broadband waves to the plasma occurs through field-aligned electron acceleration, transverse ion acceleration, and Joule heating. These processes are shown to result in precipitating electron fluxes sufficient to drive bright aurora and cause outflows of energized electrons and O + ions from the ionosphere into the low-latitude boundary layer. By solving an eigenmode equation for Alfvén waves in the observed plasma environment, it is shown that the broadband waves observed at Cluster and FAST are dispersive Alfvén waves. It is demonstrated that these waves have wavelengths perpendicular to the geomagnetic field extending from significant fractions of an L shell down to ion gyroradii and electron inertial lengths and wave frequencies in the plasma frame from 1 mHz up to 50 mHz. These waves are shown to have wavelengths along the geomagnetic field of the order of the field line length between the ionosphere and the equatorial plane and become field line resonances (FLRs) when on closed field lines. It is shown that the inclusion of nonlinear and/or nonlocal kinetic effects is required in the description of these waves to account for accelerated particles observed. On the basis of the wave polarization and spectral properties observed from Cluster and FAST it is speculated that these waves are generated through the mode conversion of surface Alfvén waves driven by tailward flows in the low-latitude boundary layer. Citation: Chaston, C. C., et al. (2005), Energy deposition by Alfvén waves into the dayside auroral oval: Cluster and FAST observations,
During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with ampl... more During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with amplitudes up to more than ~240 mV/m were observed by the Time Domain Sampler of the STEREO S/Waves instrument. These waves are an order of magnitude larger than previously been observed for whistlers in the radiation belt.
1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of ... more 1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of energy into the auroral ionosphere from broadband ULF waves in the cusp and low-latitude boundary layer. A comparison of the wave Poynting flux with particle energy and flux at both satellites indicates that energy transfer from the broadband waves to the plasma occurs through field-aligned electron acceleration, transverse ion acceleration, and Joule heating. These processes are shown to result in precipitating electron fluxes sufficient to drive bright aurora and cause outflows of energized electrons and O + ions from the ionosphere into the low-latitude boundary layer. By solving an eigenmode equation for Alfvén waves in the observed plasma environment, it is shown that the broadband waves observed at Cluster and FAST are dispersive Alfvén waves. It is demonstrated that these waves have wavelengths perpendicular to the geomagnetic field extending from significant fractions of an L shell down to ion gyroradii and electron inertial lengths and wave frequencies in the plasma frame from 1 mHz up to 50 mHz. These waves are shown to have wavelengths along the geomagnetic field of the order of the field line length between the ionosphere and the equatorial plane and become field line resonances (FLRs) when on closed field lines. It is shown that the inclusion of nonlinear and/or nonlocal kinetic effects is required in the description of these waves to account for accelerated particles observed. On the basis of the wave polarization and spectral properties observed from Cluster and FAST it is speculated that these waves are generated through the mode conversion of surface Alfvén waves driven by tailward flows in the low-latitude boundary layer. Citation: Chaston, C. C., et al. (2005), Energy deposition by Alfvén waves into the dayside auroral oval: Cluster and FAST observations,
We report observations by Mars Global Surveyor (MGS) of thousands of peaked electron energy spect... more We report observations by Mars Global Surveyor (MGS) of thousands of peaked electron energy spectra similar to terrestrial auroral electrons. They are observed on the Martian nightside, near strong crustal magnetic sources. The spectra have peak energies ranging from 100 eV - 2.5 keV, and fluxes near the peak are 10-10000 times higher than typical nightside spectra. They occur on magnetic field lines that connect the shocked solar wind to crustal magnetic fields, and on adjacent closed field lines. Their detection is directly controlled by the solar wind, suggesting that magnetic reconnection is required for their observation. We calculate that the most energetic distributions could produce atmospheric emission with intensity comparable to that recently reported from the Mars Express (MEX) spacecraft. Half of the most energetic examples occur during the passage of space weather events past Mars, suggesting that a disturbed plasma environment is favorable for electron acceleration along magnetic field lines.
During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with ampl... more During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with amplitudes up to more than ~240 mV/m were observed by the Time Domain Sampler of the STEREO S/Waves instrument. These waves are an order of magnitude larger than previously been observed for whistlers in the radiation belt.
During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with ampl... more During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with amplitudes up to more than ~240 mV/m were observed by the Time Domain Sampler of the STEREO S/Waves instrument. These waves are an order of magnitude larger than previously been observed for whistlers in the radiation belt.
1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of ... more 1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of energy into the auroral ionosphere from broadband ULF waves in the cusp and low-latitude boundary layer. A comparison of the wave Poynting flux with particle energy and flux at both satellites indicates that energy transfer from the broadband waves to the plasma occurs through field-aligned electron acceleration, transverse ion acceleration, and Joule heating. These processes are shown to result in precipitating electron fluxes sufficient to drive bright aurora and cause outflows of energized electrons and O + ions from the ionosphere into the low-latitude boundary layer. By solving an eigenmode equation for Alfvén waves in the observed plasma environment, it is shown that the broadband waves observed at Cluster and FAST are dispersive Alfvén waves. It is demonstrated that these waves have wavelengths perpendicular to the geomagnetic field extending from significant fractions of an L shell down to ion gyroradii and electron inertial lengths and wave frequencies in the plasma frame from 1 mHz up to 50 mHz. These waves are shown to have wavelengths along the geomagnetic field of the order of the field line length between the ionosphere and the equatorial plane and become field line resonances (FLRs) when on closed field lines. It is shown that the inclusion of nonlinear and/or nonlocal kinetic effects is required in the description of these waves to account for accelerated particles observed. On the basis of the wave polarization and spectral properties observed from Cluster and FAST it is speculated that these waves are generated through the mode conversion of surface Alfvén waves driven by tailward flows in the low-latitude boundary layer. Citation: Chaston, C. C., et al. (2005), Energy deposition by Alfvén waves into the dayside auroral oval: Cluster and FAST observations,
During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with ampl... more During a passage through the Earth's dawn-side outer radiation belt, whistlermode waves with amplitudes up to more than ~240 mV/m were observed by the Time Domain Sampler of the STEREO S/Waves instrument. These waves are an order of magnitude larger than previously been observed for whistlers in the radiation belt.
1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of ... more 1] We report in situ observations from the Cluster and FAST spacecraft showing the deposition of energy into the auroral ionosphere from broadband ULF waves in the cusp and low-latitude boundary layer. A comparison of the wave Poynting flux with particle energy and flux at both satellites indicates that energy transfer from the broadband waves to the plasma occurs through field-aligned electron acceleration, transverse ion acceleration, and Joule heating. These processes are shown to result in precipitating electron fluxes sufficient to drive bright aurora and cause outflows of energized electrons and O + ions from the ionosphere into the low-latitude boundary layer. By solving an eigenmode equation for Alfvén waves in the observed plasma environment, it is shown that the broadband waves observed at Cluster and FAST are dispersive Alfvén waves. It is demonstrated that these waves have wavelengths perpendicular to the geomagnetic field extending from significant fractions of an L shell down to ion gyroradii and electron inertial lengths and wave frequencies in the plasma frame from 1 mHz up to 50 mHz. These waves are shown to have wavelengths along the geomagnetic field of the order of the field line length between the ionosphere and the equatorial plane and become field line resonances (FLRs) when on closed field lines. It is shown that the inclusion of nonlinear and/or nonlocal kinetic effects is required in the description of these waves to account for accelerated particles observed. On the basis of the wave polarization and spectral properties observed from Cluster and FAST it is speculated that these waves are generated through the mode conversion of surface Alfvén waves driven by tailward flows in the low-latitude boundary layer. Citation: Chaston, C. C., et al. (2005), Energy deposition by Alfvén waves into the dayside auroral oval: Cluster and FAST observations,
We report observations by Mars Global Surveyor (MGS) of thousands of peaked electron energy spect... more We report observations by Mars Global Surveyor (MGS) of thousands of peaked electron energy spectra similar to terrestrial auroral electrons. They are observed on the Martian nightside, near strong crustal magnetic sources. The spectra have peak energies ranging from 100 eV - 2.5 keV, and fluxes near the peak are 10-10000 times higher than typical nightside spectra. They occur on magnetic field lines that connect the shocked solar wind to crustal magnetic fields, and on adjacent closed field lines. Their detection is directly controlled by the solar wind, suggesting that magnetic reconnection is required for their observation. We calculate that the most energetic distributions could produce atmospheric emission with intensity comparable to that recently reported from the Mars Express (MEX) spacecraft. Half of the most energetic examples occur during the passage of space weather events past Mars, suggesting that a disturbed plasma environment is favorable for electron acceleration along magnetic field lines.
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Papers by Mary Acuña