Slide1: IONOSPHERIC DISTURBANCE IN THE EQUATORIAL REGION DURING INTENSE MAGNETIC STORMS Santi Basu1 and Sunanda Basu2 1Space Vehicles Directorate, Air Force Research Laboratory, Hanscom AFB, MA 01731, USA; 2Center for Space Physics, Boston University, Boston, MA 02215; LWS GEOSTORM CDAW AND CONFERENCE Florida Institute of Technology, Melbourne, Florida 6 March 2007


Questions: Questions How prompt are the responses of the mid-latitude and the equatorial ionosphere to superstorms? Can we consider the prompt penetration phase to correspond to the interval between the rapid decrease of Dst (> 50 nT/hr) to Dst min? Can we specify the longitude of equatorial ionospheric disturbances (bubbles and bite-outs) from a knowledge of Dst variations?


Slide3: Plasma Structuring in the Middle and Equatorial Ionosphere During the Halloween Storm Near-Simultaneous Electric Field Penetration from High to Low Latitudes During Intense Magnetic Storms Impulsive Generation of Scintillation at Mid-Latitudes and Specific Equatorial Longitudes with Westward Transport (S. Basu et al., GRL, 2005)


IMF BZ AND SYM-H VARIATION DURING OCTOBER 30-31, 2003 STORM: IMF BZ AND SYM-H VARIATION DURING OCTOBER 30-31, 2003 STORM


Slide5: A A B B C C Deep Equatorial Plasma Depletions and Contiguous Bubble-Free Equatorial Anomaly Regions with Enhanced Ionization in the South Atlantic/ South American Sector During Oct 30-31 Storm


Spectacular Increase of Ionospheric Height at Magnetic Equator and Anomaly Locations in Brazil : Spectacular Increase of Ionospheric Height at Magnetic Equator and Anomaly Locations in Brazil


IMF BZ AND SYM-H VARIATION DURING 20 NOVEMBER 2003 STORM: IMF BZ AND SYM-H VARIATION DURING 20 NOVEMBER 2003 STORM


Slide8: A A B B C C D D Deep Equatorial Plasma Depletions and Contiguous Bubble-Free Equatorial Anomaly Regions with Enhanced Ionization in the African/Brazilian Sector During 20 Nov 2003 Storm


Slide9: Note that Dst Min Phase coincides with that of Bz south


Slide10: Equatorial Bubbles Ground and Space Observations of scintillations and plasma bubbles on May 15, 2005 Scintillation at Kwaj at 165 E and Equatorial Bubbles from DMSP F-15 seen only within 160-190 E, which is in the dusk sector during main phase of the storm Long Longitude 165 E


Slide11: Note that Dst Min is reached when Bz is Northward.


Slide12: Westward drifts>100 m/s Ground and Space Observations of scintillations and plasma bubbles on Aug 24,2005 Scintillation at Guam at 145 E and Equatorial Bubbles from DMSP F-15 seen only within 120-150 E, which is in the dusk sector during the main phase of the storm Equatorial Bubbles Large westward drifts>100m/s


STATISTICS OF THE RESPONSE OF THE EQUATORIAL IONOSPHERE TO INTENSE MAGNETIC STORMS: STATISTICS OF THE RESPONSE OF THE EQUATORIAL IONOSPHERE TO INTENSE MAGNETIC STORMS Intense Magnetic Storms: d Dst/dt > 50 nT/hr and Dst min 50 nT/hr, (UT)3 marks the time of Dst min , and (UT)2 is close to the middle of the interval The Dusk Sector Corresponded to 20-21 LT Equatorial Disturbance at Dusk corresponding to (UT)1: 10 storms Equatorial Disturbance at Dusk corresponding to (UT)2: 18 storms Equatorial Disturbance at Dusk corresponding to (UT)3: 7 storms


Slide14: Near simultaneous onset of scintillation at sub-auroral and equatorial locations during superstorms indicate direct penetration (DP) of eastward electric fields from high latitudes to the equatorial ionosphere. The time interval of DP electric field can be reckoned from the time of the rapid decrease of SYM-H to the time of minimum SYM-H. The penetration electric field and the F-region neutral wind dynamo combine to cause bubbles at dusk corresponding to the main phase of the storm. - The 30 October 2003 storm with main phase between 2130 UT and 2315 UT caused plasma bubbles and bite-outs at dusk in the Atlantic / Brazilian sector, - The 20 November 2003 storm with earlier time of minimum SYM-H (around 18 UT) caused post-sunset bite-outs further east in the Atlantic/African sector. - The storms of 15 May 2005 and 24 August 2005 with main phase between 7 – 9 UT and 10 – 12 UT respectively caused disturbances still further east in the Pacific around Kwajalein and Guam respectively. Summary