Magnetosphere-Ionosphere-Thermosphere-Mesosphere (M-ITM) meeting
Wednesdays @ 10:30am, Building 21, Room 183B
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15 November 2017, Building 21, Room 183B @ 10:30am
Speaker: Akhush Bhaskar (674, University Corporation for Atmospheric Research)
Title: Global ground-magnetometers response to negative pressure impulse
Abstract:
The geomagnetic field response to a moderate-amplitude negative sudden impulse (SI-) that occurred on 14 May 2009 at 10:30 UT was examined at 97 geomagnetic observatories situated all over the globe. The response signature contains a contribution from magnetospheric as well as ionospheric currents. The main impulse (MI) is defined as the maximum depression in the observed geomagnetic field. It is observed that for low-to-high latitudes, the amplitude of the MI is larger in the afternoon to post-dusk sector than in the dawn-noon sector, indicating asymmetry in the MI amplitude. We estimated the contribution at various observatories due to the Chapman-Ferraro magnetopause currents using the Tsyganenko model (T01) and subtracted this from the observed MI amplitude to obtain the contribution due to ionospheric currents. It is found that the ionospheric currents contribute significantly to the MI amplitude of moderate SI− even at low-to-mid latitudes and that the contribution is in the same direction as that from the magnetopause currents near dusk and in the opposite direction near dawn. The equivalent current vectors reveal a clockwise (anticlockwise) ionospheric current loop in the afternoon (morning) sector during the MI of the negative pressure impulse. This evidences an ionospheric twin-cell-vortex current system (DP2) due to field-aligned currents (FACs) associated with the dusk-to-dawn convection electric field during the MI of an SI−. In addition, the summer hemisphere reveals larger MI amplitudes than the winter hemisphere, indicating once again the role of ionospheric currents.
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01 November 2017, Building 21, Room 183B @ 10:30am
Speaker: David Mackler, NASA/GSFC (673), Catholic University of America
Title: An observational study of the relationship between precipitating ions and Energetic Neutral Atoms emerging from the ion/atmosphere interaction region
Abstract:
Plamasheet particles transported Earthward during times of active magnetic convection can interact with thermospheric neutrals through charge exchange. The resulting ENAs are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low altitude (300-800 km) ion precipitation in the high latitude inner mangetosphere are termed Low Altitude Emissions (LAEs). LAEs are highly non-isotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90 degrees. The observed Geomagnetic Emission Cone (GEC) of LAEs can be mapped spatially, showing where energy is deposited during storm/sub-storm times. In this study we present a statistical look at the correlation between LAE flux and geomagnetic activity. The LAE data is from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000-2005). The SYM-H, AE, and Kp indices are used for geomagnetic activity. Results indicate a general non-linear enhancement to LAE flux for all three indices. The MLT distribution of LAEs are centered about midnight, indicating a plasmasheet source.
[talk file | paper link/file]
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17 October 2017, Building 21, Room 183B @ 3:00pm
Speaker: Vladimir Airapetian, NASA/GSFC (671), American University
Title: Atmospheric Beacons of Life from Exoplanets Around G and K Stars
Abstract:
The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitable worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen- oxygen rich terrestrial-type exoplanets including molecular oxygen (O2), ozone (O3), water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments. In this paper we propose to use the powerful emission from rotational-vibrational bands of nitric oxide, hydroxyl and molecular oxygen as signatures of nitrogen, oxygen, and water rich atmospheres of terrestrial type exoplanets “highlighted” by the magnetic activity from young G K and M main-sequence stars. The signals from these fundamental chemical prerequisites of life we call atmospheric “beacons of life” create a unique opportunity to perform direct imaging observations of Earth-sized exoplanets with high signal-to-noise and low spectral resolution with the upcoming NASA missions.
[talk file | paper link/file]
15 November 2017, Building 21, Room 183B @ 10:30am
Speaker: Akhush Bhaskar (674, University Corporation for Atmospheric Research)
Title: Global ground-magnetometers response to negative pressure impulse
Abstract:
The geomagnetic field response to a moderate-amplitude negative sudden impulse (SI-) that occurred on 14 May 2009 at 10:30 UT was examined at 97 geomagnetic observatories situated all over the globe. The response signature contains a contribution from magnetospheric as well as ionospheric currents. The main impulse (MI) is defined as the maximum depression in the observed geomagnetic field. It is observed that for low-to-high latitudes, the amplitude of the MI is larger in the afternoon to post-dusk sector than in the dawn-noon sector, indicating asymmetry in the MI amplitude. We estimated the contribution at various observatories due to the Chapman-Ferraro magnetopause currents using the Tsyganenko model (T01) and subtracted this from the observed MI amplitude to obtain the contribution due to ionospheric currents. It is found that the ionospheric currents contribute significantly to the MI amplitude of moderate SI− even at low-to-mid latitudes and that the contribution is in the same direction as that from the magnetopause currents near dusk and in the opposite direction near dawn. The equivalent current vectors reveal a clockwise (anticlockwise) ionospheric current loop in the afternoon (morning) sector during the MI of the negative pressure impulse. This evidences an ionospheric twin-cell-vortex current system (DP2) due to field-aligned currents (FACs) associated with the dusk-to-dawn convection electric field during the MI of an SI−. In addition, the summer hemisphere reveals larger MI amplitudes than the winter hemisphere, indicating once again the role of ionospheric currents.
-------------------------------------------------------------------------------------------------------------------------
01 November 2017, Building 21, Room 183B @ 10:30am
Speaker: David Mackler, NASA/GSFC (673), Catholic University of America
Title: An observational study of the relationship between precipitating ions and Energetic Neutral Atoms emerging from the ion/atmosphere interaction region
Abstract:
Plamasheet particles transported Earthward during times of active magnetic convection can interact with thermospheric neutrals through charge exchange. The resulting ENAs are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low altitude (300-800 km) ion precipitation in the high latitude inner mangetosphere are termed Low Altitude Emissions (LAEs). LAEs are highly non-isotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90 degrees. The observed Geomagnetic Emission Cone (GEC) of LAEs can be mapped spatially, showing where energy is deposited during storm/sub-storm times. In this study we present a statistical look at the correlation between LAE flux and geomagnetic activity. The LAE data is from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000-2005). The SYM-H, AE, and Kp indices are used for geomagnetic activity. Results indicate a general non-linear enhancement to LAE flux for all three indices. The MLT distribution of LAEs are centered about midnight, indicating a plasmasheet source.
[talk file | paper link/file]
-------------------------------------------------------------------------------------------------------------------------
17 October 2017, Building 21, Room 183B @ 3:00pm
Speaker: Vladimir Airapetian, NASA/GSFC (671), American University
Title: Atmospheric Beacons of Life from Exoplanets Around G and K Stars
Abstract:
The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitable worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen- oxygen rich terrestrial-type exoplanets including molecular oxygen (O2), ozone (O3), water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments. In this paper we propose to use the powerful emission from rotational-vibrational bands of nitric oxide, hydroxyl and molecular oxygen as signatures of nitrogen, oxygen, and water rich atmospheres of terrestrial type exoplanets “highlighted” by the magnetic activity from young G K and M main-sequence stars. The signals from these fundamental chemical prerequisites of life we call atmospheric “beacons of life” create a unique opportunity to perform direct imaging observations of Earth-sized exoplanets with high signal-to-noise and low spectral resolution with the upcoming NASA missions.
[talk file | paper link/file]