Transcript Slide 1
What DMSP Data Tell us About the Thermosphere Response to Solar Wind Forcing Delores Knipp CU Aerospace Engineering Sciences and NCAR HAO With Assistance from Liam Kilcommons, CSU What DMSP Data Tell us About the Thermosphere Response to Solar Wind Forcing - Energy deposition on the dayside can be strongly controlled by the IMF By component -Even during strong storms energy deposition on the dayside may exceed that on the nightside -Orbit Integrated Poynting flux (and DMSP B) show the physical link between solar wind and neutral density periodicities - During strong IMF By events magnetosheath particles are supplementing the energy deposition by Poynting flux…..but at a different altitude - During high speed streams energy deposition on the dayside dominates that on the nightside Schematics of magnetopause reconnection for IMF Bz illustrating the topological differences in reconnection location, depending upon the interplanetary magnetic field direction. Southward IMF Adapted from Day, C., Spacecraft probes the site of magnetic reconnection in Earth's magnetotail, Physics Today, Vol. 54, No. 10, 16-17, 2001. Northward IMF Adapted from NASA Press release: Connection of Sun's and Earth's magnetic fields provides energy for auroras, space weather, 2000. 0 Merging location simulation 270 with dipole tilt of 30, IMF Bz = –5 nT, and IMF By = 5 nT. Park et al., 2006 90 180 When IMF Bz is negative and By is present Merged flux tubes are accelerated azimuthally, Dayside flow channel s develop between convections cells R1 field aligned currents become asymmetric near noon - Positive (duskward) east, – Negative (dawnward) west, Those connected to the southern (northern) hemisphere move duskward (dawnward) Those connected to the southern (northern) hemisphere move dawnward (duskward) 0 N 270 0 N 90 180 270 90 180 (Weimer, 2005 and Anderson, et al. 2008) Downward R1 currents dominate the noon sector in the northern hemisphere Upward R1 currents dominate the noon sector in the northern hemisphere When IMF Bz is positive and By is present Merged flux tubes are accelerated azimuthally, Dayside flow channel s develop but appear to be more variable R1 field aligned currents become asymmetric near noon , R0 field aligned currents may be present Strong IMF and high speed flow may provide more clarity 0 0 270 270 90 90 180 180 (Weimer, 2005 and Anderson, et al. 2008) Poynting Vector from Defense Meteorological Satellite Program S/C DMSP instruments sense Electric and Magnetic Fields Y Spacecraft track X Z S E B DMSP Horizontal / 0 S|| ( E xB y E yBx ) / 0 where E V B IGRF and B DMSP Horizontal B DMSP B Main Near-Cusp energy source during strong IMF By: Li et al. 0 270 Cusp reconnection near the dawn flank Southern lobe field lines 90 180 SH Field lines map across dayside SH OPENGGCM Joule Heating SH Calculated DMSP Poynting Flux Bz ~+10nT BY ~+25nT VSW ~ 950 km/s OPENGGCM FAC Obs DMSP Mag Perturbations DMSP Data and Calculations Delta Bx Vy Delta By Poynting Flux Aug 24 2005 Large IMF By, Bz~0 Neutral Density Crowley et al., 2010 DMSP Data and Calculations Poynting Flux Particle Flux ….not quite the full story….. Vz High-Latitude Energy Input: Field and Particles Poynting Flux Particle Flux DMSP Data and Calculations Poynting Flux Particle Flux ….not quite the full story….. Vz Poynting Flux and Solar Wind Speed 2005 Lomb-Scargle Periodogram DMSP F-15 Orbit Integrated |dBy| for 2005 Orbit Integrated dBy Blue = angles in the range 90-180 , typical away or positive polarity. Red denotes angles in the range 270-360 ., typical toward or negative polarity. Yellow denotes angles in either of the other two azimuthal quadrants. DMSP F-15 Orbit Integrated dBy for 2005 Orbit Integrated dBy Blue = angles in the range 90-180 , typical away or positive polarity. Red denotes angles in the range 270-360 ., typical toward or negative polarity. Yellow denotes angles in either of the other two azimuthal quadrants. Intense Magnetic Storm Jan 21-22 2005 High-speed Stream August 15-16 2005 AMIE Joule Heating and Electric Potential During High Speed Flow 00 UT 16 Aug 2005 Courtesy of G. Crowley AMIE Joule Heating and Electric Potential During High Speed Flow 04 UT 16 Aug 2005 Courtesy of G. Crowley AMIE Joule Heating and Electric Potential During High Speed Flow 1040 UT 16 Aug 2005 Courtesy of G. Crowley AMIE Joule Heating and Electric Potential During High Speed Flow 2045 UT 16 Aug 2005 Courtesy of G. Crowley What DMSP Data Tell us About the Thermosphere Response to Solar Wind Forcing - Energy deposition on the dayside is strongly controlled by the IMF By component -Even during strong storms energy deposition on the dayside may exceed that on the nightside -Orbit Integrated Poynting flux (and DMSP B) show the physical link between solar wind and neutral density periodicities - During strong IMF By events magnetosheath particles are supplementing the energy deposition by Poynting flux…..but at a different altitude - During high speed streams energy deposition on the dayside dominates that on the nightside