Physics – Plasma Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufmsm41b1725s&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #SM41B-1725
Physics
Plasma Physics
[7800] Space Plasma Physics, [7859] Space Plasma Physics / Transport Processes
Scientific paper
Recent work has shown that ionospheric convection flow experiences dramatic changes during Poleward Boundary Intensifications (PBIs) and substorms and there are indications for distinct flow patterns for these two phenomena. In this study, we used observations from the IMAGE satellite FUV imager to identify clear and distinct PBI and substorm events. We then examined Sondrestrom incoherent scattered radar flows observed during the events identified with IMAGE FUV and at the same local time sector in order to identify the temporary variation of the ionospheric flow signatures associated with PBIs and substorms. We find distinct differences between the convection flow patterns of the two phenomena. For substorms, there is clear flow enhancement in the eastward direction before the onset. After onset, the magnitude of that eastward flow dramatically decreases and the direction suddenly changes to westward. For PBIs, there is clear enhancement of flow during the PBI with dominant equatorward component at the poleward boundary of the auroal oval. We then used the SuperDARN HF radar observation during our events to examine the spatial structure of ionospheric flows associated with PBIs and substorms. For substorms, our results show the enhancement of eastward flow at high latitude and sometimes turning to westward at lower latitudes before onset. After onset, the flow suddenly turns to westward at all latitudes. For PBIs, there is clear flow enhancement with dominant equatorward component at the poleward boundary of the auroal oval. Using the IMAGA FUV images and electron density observations from the Sondrestrom radar, we can reliably determine the open-close filed line boundary for our cases. We found that for PBIs flows are typically enhanced around the open-close field line boundary, while for substorms flow enhancement before onset can occur both at lower latitude or near the separatrix .
Frey Harald U.
Lyons Larry R.
Mende Stephen B.
Shi Yaoming
Zesta Eftyhia
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