Observations in the vicinity of substorm onset: Implications for the substrom process

Details Observations in the vicinity of substorm onset: Implications for the substrom process Observations in the vicinity of substorm onset: Implications for the substrom process

May 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995jgr...100.7937e&link_type=abstract

Journal of Geophysical Research (ISSN 0148-0227), vol. 100, no. A5, p. 7937-7969

Physics

Geophysics

63

Auroras, Earth Magnetosphere, Geophysics, Ionospheric Storms, Geomagnetic Pulsations, Geomagnetism, Geosynchronous Orbits, Magnetic Storms, Solar Wind, Stability

Scientific paper

Multi-instrument data sets from the ground and satellites at both low and high altitude have provided new results concerning substorm onset and its source region in the magnetosphere. Twenty-six out of 37 substorm onset events showed evidence of azimuthally spaced auroral forms (AAFs) prior to the explosive poleward motion associated with optical substorm onset. AAFs can span 8 hours of local time prior to onset and generally propagate eastward in the morning sector. Onset itself is, however, more localized spanning only about 1 hour local time. AAF onset occur during time periods when the solar wind pressure is relatively high. AAFs brighten in conjunction with substorm onset leading to the conclusion that they are a growth phase activity casually related to substorm onset. Precursor activity associated with these AAFs is also seen near geosynchronous orbit altitude and examples show the relationship between the various instrumental definitions of substorm onset. The implied mode number (30 to 135) derived from this work is inconsistent with cavity mode resonances but is consistent with a modified flute/ballooning instability which requires azimuthal pressure gradients. The extended source region and the distance to the open-closed field line region constrain reconnection theory and local mechanisms for substorm onset. It is demonstrated that multiple onset substorms can exist for which localized dipolarizations and the Pi 2 occur simultaneously with tail stretching existing elsewhere. These pseudobreakups can be initiated by auroral streamers which originate at the most poleward set of arc systems and drift to the more equatorward main UV oval. Observations are presented of these AAFs in conjunction with low- and high-altitutde particle and magnetic field data. These place the activations at the interface between dipolar and taillike field lines probably near the peak in the cross-tail current. These onsets are put in the context of a new scenario for substorm morphology which employs individual modules which operate independently or couple together. This allows particular substorm events to be more accurately described and investigated.

Affiliated with

Also associated with

No associations

Rating

Observations in the vicinity of substorm onset: Implications for the substrom process does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Observations in the vicinity of substorm onset: Implications for the substrom process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Observations in the vicinity of substorm onset: Implications for the substrom process will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1061308