Evidence for Dayside Interhemispheric FieldAligned Currents During Strong

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Evidence for Dayside Interhemispheric Field-Aligned Currents During Strong IMF By Conditions Seen by Super.

Evidence for Dayside Interhemispheric Field-Aligned Currents During Strong IMF By Conditions Seen by Super. DARN Radars Joseph B. H. Baker, Bharat Kunduri and J. Michael Ruohoniemi Center for Space Science and Engineering Research (Space@VT) Virginia Tech Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

The Super. DARN Radars The Super Dual Auroral Radar Network (Super. DARN) is an

The Super. DARN Radars The Super Dual Auroral Radar Network (Super. DARN) is an international network of high-frequency (HF) radars for researching the Earth’s upper atmosphere, ionosphere, and connection into geospace. Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

Interhemispheric FACs A strong IMF By component will penetrate the dayside magnetosphere and produce

Interhemispheric FACs A strong IMF By component will penetrate the dayside magnetosphere and produce interhemispheric field-aligned currents (FACs) [Kozlovsky et al. , 2003]. l For a strong negative IMF By component: NORTHERN HEMISPHERE: l Downward FAC in polar cap l Outward FAC in closed field-line region l Eastward auroral zone convection SOUTHERN HEMISPHERE: l Upward FAC in polar cap l Downward FAC in closed field line region l Westward auroral zone convection l From Kozlovsky et al. [2003] Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

20050529 0240 UT Southern Hemisphere (Winter) Northern Hemisphere (Summer) Afternoon convection is stronger in

20050529 0240 UT Southern Hemisphere (Winter) Northern Hemisphere (Summer) Afternoon convection is stronger in the southern (winter) hemisphere (left panel) l Interplanetary Magnetic Field (IMF) is southward with negative By component l Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

20050529 0240 UT Southern Hemisphere (Winter) Northern Hemisphere (Summer) Southern Hemisphere: Field-aligned currents reinforce

20050529 0240 UT Southern Hemisphere (Winter) Northern Hemisphere (Summer) Southern Hemisphere: Field-aligned currents reinforce afternoon convection l Northern Hemisphere: Field-aligned currents counteract afternoon convection l Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

20050216 1330 UT Southern Hemisphere (Summer) Northern Hemisphere (Winter) Afternoon convection is stronger in

20050216 1330 UT Southern Hemisphere (Summer) Northern Hemisphere (Winter) Afternoon convection is stronger in the southern (summer) hemisphere (left panel) l Interplanetary Magnetic Field (IMF) is southward with negative By component l Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

20050216 1330 UT Southern Hemisphere (Summer) Northern Hemisphere (Winter) Southern Hemisphere: Field-aligned currents reinforce

20050216 1330 UT Southern Hemisphere (Summer) Northern Hemisphere (Winter) Southern Hemisphere: Field-aligned currents reinforce afternoon convection l Northern Hemisphere: Field-aligned currents counteract afternoon convection l Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

Velocity Differences l Southern hemisphere velocities (left) are mapped into the northern hemisphere (middle)

Velocity Differences l Southern hemisphere velocities (left) are mapped into the northern hemisphere (middle) and compared with northern hemisphere velocities (right). l The velocities are clearly higher at the southern footpoints of the closed flux tubes. Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

Current Density (n. A/m 2) Estimated FAC Magnitudes l The interhemispheric velocity differences are

Current Density (n. A/m 2) Estimated FAC Magnitudes l The interhemispheric velocity differences are used to estimate the FAC magnitude. Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

Width of the FAC Channel Blue = southern velocities Black = northern velocities Feb

Width of the FAC Channel Blue = southern velocities Black = northern velocities Feb 16 th 2005 May 29 th, 2005 l The FAC channels are 3 -6° wide and the velocity difference is strongest at high latitudes. l The velocity difference also decreases moving from noon toward dusk. Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

Summary l During two event periods with strong negative IMF By component, Super. DARN

Summary l During two event periods with strong negative IMF By component, Super. DARN radars observed strong interhemispheric asymmetries in the afternoon sunward convection on closed magnetic field lines. l The observations are consistent with interhemispheric field-aligned currents (FACs) flowing out of the northern hemisphere and into the southern hemisphere on closed magnetic field lines [Kozlovsky et al. , 2003]. l Estimates for the strength of the FACs have been calculated and the latitudinal width of the FAC channel was found to be 3 -6 degrees wide. l The intensity of the FACs decreased moving equatorward from the openclosed field line boundary and moving from noon toward later local times. Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

Joseph Baker (jo. baker@vt. edu) Virginia Tech Super. DARN 2012 GEM Workshop

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Surface Currents and Deep Currents Currents Current ASurface Currents and Deep Currents Currents Current A
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Currents and Climates Notes Surface Currents Surface currentsCurrents and Climates Notes Surface Currents Surface currents
Deep Currents Deep Currents What are deep currentsDeep Currents Deep Currents What are deep currents
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