Solar Flare Effects on the Ionosphere 
 
1Bruce T. Tsurutani, 1Anthony J. Mannucci and 2Olga P. Verkhoglyadova 
 
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 
91109 
2IGPP, University of California at Riverside, Riverside, CA 
 
Solar flare photons range from visible to x-rays and even shorter wavelengths. 
It is the EUV and x-ray photons which affect the ionosphere the most. 
Photoionization by flare EUV and x-rays have been observed to increase total 
electron content (TEC) by 30% within ~ 5 minutes. Different wavelength photons 
affect different height layers of the ionosphere.  We will discuss the 
Halloween 2003 flares as examples. These solar events were some of the largest 
on record. The November 4, 2003 flare was rated as a X28 flare.  However the 
lesser intensity October 28, 2003 X17 flare had a larger ionospheric effect. 
Why? We will discuss how ionospheric researcher can use solar data to perform 
solar-ionospheric studies.  We will identify some of the important pitfalls that 
researchers should avoid. Ions and electrons of up to hundreds of MeV energy are 
associated with solar flares.  Some are produced at the flare sites (called 
prompt particles) and others are believed to be accelerated at coronal mass 
ejection (CME) fast forward shocks in the interplanetary medium. Some basic 
comments will be made about shock acceleration mechanisms and connectivity to Earth.